Color-Coded for Your Convenience

"Miko: How can you be so certain it was evil, though? [...]

Roy: Ummm... its scales weren't all shiny?

Miko: Ah. Then its destruction was just and necessary.

Elan: Dragons, color-coded for YOUR convenience!"

- Order of the Stick, strip #207

Vision is the one sense we humans rely on the most. We usually identify things by sight rather than sound or smell. It is for this reason that creators of visual media will make sure that things look different enough for the audience to easily recognize and tell apart. It can also be a form of visual shorthand for characterization, so that the audience can tell certain things about a character or setting without having to be told.

In addition, to the audience, this trope may be used in-Universe so that the characters can easily tell the difference between groups or things.

One way to do this is to use colour as an indicator that two things are different (when using different colours) or two things belong to the same category (when using the same colours). Colour can indicate who is the good guy and who is the bad guy, they can indicate personality type, they can say things about gameplay elements in a video game, which organization or group the person belongs to, and so on.

Compare Good and Evil For Your Convenience. See also Sound Coded for Your Convenience, for when objects, characters, and actions can be discerned better by the sounds they make.

Sub Tropes:
Categories:
 * Hair Colors


 * Amazing Technicolor Population
 * Bring My Red Jacket
 * Color Character
 * Color Coded Armies
 * Color Coded Characters
 * Chromatic Arrangement
 * Rainbow Motif
 * Color Coded Elements
 * Elemental Eye Colors
 * Elemental Hair
 * Elemental Nation
 * Color Coded Multiplayer
 * Color Coded Patrician
 * Color Coded Secret Identity
 * Colour Coded Timestop
 * Color Coded Wizardry
 * Common Eye Colors
 * Convenient Color Change
 * Good Colors Evil Colors
 * Black Eyes of Evil
 * Blondes Are Evil
 * Blond Guys Are Evil
 * Dark Is Evil
 * Evil Redheads
 * Eyes of Gold
 * Paint It Black
 * Red and Black And Evil All Over
 * Red Eyes Take Warning
 * Womanin Black
 * Lady in Red
 * Law of Chromatic Superiority
 * Man in White
 * Morphic Resonance
 * Pink Girl Blue Boy
 * Powerup Full Color Change
 * Rainbow Speak
 * Red Oni Blue Oni
 * White Shirt of Death
 * Woman in White

Please only list examples that do not fall under one of the above subtropes.

Fan Fiction

 * In Clouded Sky, there are temples dedicated to each Pokémon type, and the acolytes of the temples dress in colors that correspond with the type their temple represents (Fire Temple = Red, Water Temple = Blue, etc.).

Films

 * Wall Street: Money Never Sleeps. All of the characters wear suits in morally ambiguous shades of grey. The villain, Bretton James, wears a demonic red suit.
 * In Rebel Without a Cause, the color red is used often as a motif. For example, Judy's coat at the beginning of the movie, Jim's jacket, one of Plato's socks, etc.
 * Guillermo Del Toro's vision for The Hobbit included eight color-coded "seasons" (middle of third paragraph).
 * Toy Story 3: Blue = safe (Andy's room; Butterfly room; ); red = unsafe ; Sickly Green Glow = corrupted.
 * Disney's Aladdin has color motifs based on its desert setting. Blue (water) = good, red (heat) = evil, and yellow (sand) = neutral.
 * In Logan's Run, the people who lived in the city wore clothes that matched their ages and the color of their life clocks. The sandmen, who were essentially portrayed as being evil, wore black and gray, even when they were in the gym or at home.
 * In The Hunt for Red October, different color lighting was used for each submarine's interior to aid the viewer in quick recognition of which submarine it was and to minimize confusion.
 * In the 1920 silent film The Mark of Zorro, Zorro instructs his allies to ride black horses on their night's mission to rescue some unjustly-jailed prisoners. The soldiers that pursue them conveniently all have light-colored horses, making it easy for viewers to keep track of which band of riders is which.
 * Tron Legacy uses this to great effect, as noted by Tobuscus.
 * Exaggerated Trope and Justified Trope in that universe, as a character's Tron Lines indicate their loyalties, position in the system, and probably act as an identifier.
 * In the Brotherhood series of films, the hero always wears white boxers, while all the other villanous characters wear black underwear.
 * As a general rule, absent any other cues like dialogue or geography (and often enough even with them), a rising sun is depicted as red and a setting sun as orange in all films. This is just a cinematographer's convention that's gone back to the early days of color film.
 * In Star Wars, this tends to overlap with Good Colors Evil Colors, such as the blue and green lightsabers of the Jedi vs. the red of the Sith (as well as their brown robes vs. black robes) and the silver and red of the Rebellion vs. the blue and black (and white) of the Empire.
 * In Kamen Rider X Super Sentai Super Hero Taisen, Kamen Rider OOO will lend his medals to the Gokaigers, allowing them to transform into OOO's combo forms. With one exception, the general coloring of OOO's combos match up with the Gokaigers' colors (red, blue, yellow, green, and white [standing in for silver]), and they transform accordingly. The exception is Gokai Pink, who instead gets the purple combo.

Folklore and Mythology

 * If an animal is important and doesn't have extra features (Pegasus, Sleipnir, Cerberus), it will most often be a certain color. White is a particularly strong giveaway, as many cultures believe that white animals have magical properties.
 * This is addressed (or lampshaded or something) in GURPS Infinite Worlds, which lists being entirely white as one of the signs that an animal may be a parachronozoid (in-world jargon for "naturally capable of moving between worlds").

Literature

 * Used in Orphans of Chaos. When using her higher senses, Amelia can see the utility of nearby objects to her or someone else by how brightly they glow with a white light.
 * Lampshaded by Diana Wynne Jones in The Tough Guide to Fantasyland, wherein she explained that a Genre Savvy character can always identify which characters are (or will turn out) good, evil, traitorous, possessing magical powers, or lost royal heirs upon first meeting them by the color of their hair or eyes (or combination thereof).
 * In Lord of the Flies, the main characters are mostly shown to be 'good' or 'evil' by their hair colour - Ralph is blond, Jack is a redhead, and Roger's hair is dark. Ralph is the most civilised of all the boys, while Jack and Roger are more quickly lost into savagery. However, Simon was dark-haired, at least in the book, but this still follows color symbolism. Black doesn't just represent evil. . He is a Christ figure, after all.
 * In Dragonriders of Pern, the dragons are visually distinguishable by gender and caste by their color. Additionally, many of the disciplines have a distinctive color that members of the guildhall wear. Miners, crafters, harpers, and healers each have a distinctive uniform color, with further variations in tone for apprentices, journeyman, and masters.
 * The Stainless Steel Rat's Revenge. The planet of Cliaand is completely militarized and every person on it has a uniform with a color appropriate to their job.
 * In Dragonlance, the Towers of Sorcery actually enforce this trope. White represents good, Black evil, and Red neutral. This is partly because the world's history has shown a need for balance between these moral axes. Extremes of corruption and piety have brought ruin to the world.
 * Subverted in one Dragonlance short story. A knight slays what he thinks is a white dragon, which are Always Chaotic Evil. It turns out, however, that the dragon in question was an albino silver dragon (silver dragons are Always Lawful Good).
 * There was a series by Garth Nix called The Seventh Tower featuring an entire caste system based on the rainbow; the more powerful a particular color in the society's magic system, the higher the rank of the corresponding caste. Everyone owned a crystal with which they could perform light-based magic; any individual could use colors and visit floors of the complex (in which the entire society lived) equal to or lesser than their own rank, but needed special dispensation to go higher in the pecking order without actually going to the trouble of earning an increase in social station. In the lowest floors was a caste of servants who weren't given a color at all, who were regarded as being not wholly dissimilar to lepers.

Live Action TV

 * On Scrubs, the medical doctors wear blue scrubs and the surgeons wear green. Nurses most often wear pink or purple and orderlies are in maroon.
 * Doctor Who:
 * Because the TARDIS is blue, that colour is often associated with the Doctor, especially the Tenth, who wore a blue suit as often as his brown one and whose sonic screwdriver had a blue light.
 * As of series 5, the New Paradigm Daleks are
 * Scientist - orange
 * Strategist - blue
 * Drone - red
 * Eternal - yellow
 * Supreme - white
 * Sons of Anarchy: While it's not prominent, the gangs display their own colours. Samcro wears a lot of blue, Mayans have green, and the One-Niners purple.
 * Star Trek:
 * In the original series, the Starfleet uniform colors for the different divisions were Command Yellow, Science Blue, and Operations Red. In Star Trek the Next Generation, though, Command and Operations switched colors.
 * There's also the colours associated with each race or nation, used in their graphics, ships, transporters, banners or on star charts (the latter is expanded on greatly in tie-in materials).
 * The Federation is a rich blue (on star charts and their seal and warp plasma).
 * The Klingons are red (on star charts and their banner, graphic displays and ship controls, warp plasma, and transporter effect).
 * Romulans are deep green (on star charts, banners and display graphics, their warp plasma, and their transporter effect).
 * Cardassians are yellow-ochre or pink (both colours were used for their weapons - pink in their first few appearances, later yellow, their transporter is yellow-ochre; on star charts, they're either yellow or pink).
 * The Dominion is purple (their warp plasma, on star charts; their graphics are purple and green).
 * Degrassi Community School introduces uniforms in Season 10 of the eponymous show, color-coded by year (Grade 12-blue, 11-red, 10-purple, 9-yellow). This holds the next year, apparently literally for the viewers' convenience - in a real school, it would make more sense for the rising students to keep their present colors with blue rotated to the incoming freshmen.
 * Uniforms in Stargate Atlantis are colour coded in a similar manner to Star Trek. Sciences are in blue, medical are in yellow, command is in red, and military are in black.
 * From Merlin: Merlin and Arthur usually wear blue and red respectively, as a near-literal example of Red Oni Blue Oni. Spirited Young Lady and Rebellious Princess Morgana wears bright, jewel-like colours such as reds, blues, purples, and greens, whilst the gentler Shrinking Violet Guinevere wears almost every shade of pastel imaginable: lavender, peach, pink, and light blue. By series four, the bad guys (Morgana, Agravaine, Helios, and ) wear black, whilst those with magical powers are usually delinated by the colour green, particularly Mordred and the other Druids, who wear green cloaks.
 * In Clue the main cast members usually wear something of "their piece"s color.
 * Awake has two realities, with the tone of the camera distinguishing them for the audience and a colored wristband distinguishing them for the protagonist.
 * The families in Game of Thrones are colour coded by hair. The Lannisters are blonde, the Baratheons are black-haired, the Targaryens are platinum, the Greyjoys are light brown-haired and the Tullys are reddish brown-haired. This is a blessing to the viewer trying to keep track of the Loads and Loads of Characters, where the politics between families is the main theme.

Music

 * Supertramp's Album Crime of the Century has this. The lyrics sheet is color coded for each of the two singers. Roger Hodgson is white, and Rick Davies is yellow.

Tabletop Games

 * The use of color to distinguish sides is so common that it's easier to note exceptions. For instance, in shogi, the pieces of the two sides are identical and distinguished by which way they're pointing.
 * For the longest time in Dungeons and Dragons, one could easily distinguish between good and evil dragons by whether or not they were metallic and shiny (good) or vividly monochromatic (evil). This was eliminated in 4th edition, though it still gives an idea of whether or not a dragon is more likely to be more "social" or more predatory.
 * Alpha Complex in Paranoia is colour coded for your inconvenience. It's almost certain that to get anywhere interesting, you'll have to cross an area outside your colour clearance. (Paint is strictly rationed and outside your clearance.)
 * Averted in Alpha State, where all comrades are Red (but some are more Red than others).
 * In a meta example, New Horizon requires two differently colored twenty-sided dice. The rulebook labels them White and Black; you can only get criticals on the black dice.

Video Games

 * In the Super Mario series, you can tell Palette Swapped enemies/generic species behavior based on color:
 * The Lumas: White (Luma), Black (Polari), Purple (Lubba), Red (flying), Orange (Co-star), Yellow (launch star), Green (green star), Blue (Lumalee Lumabop), and Pink (Hungry Luma).
 * Koopa Troopas and Paratroopas: Green (walk in straight line for Troopas, hop aimlessly for Paratroopas), Red (walk back and forth for Troopas, fly up or down or side to side for Paratroopas), Blue (kicks shells), and Yellow (flashes).
 * Goombas: Brown (on dry land), Blue (in caves), and Gray (in castles).
 * Piranha Plants: Green (hides in pipes when Mario/Luigi is near it) and Red (comes out of pipes even when Mario/Luigi is near it, but will not come out if Mario/Luigi is on top of it).
 * Cheep Cheeps: Red (faster, can jump out of water) and Gray (was changed to green in All Stars, slower, always in water).
 * Bros.: Lime (Hammer), Blue (Boomerang), Red (Fire), Green (Sledgehammer), Purple (AFHB), and Orange (Sumo).
 * Dynasty Warriors: Shu - Green, Wei - Blue, Wu - Red, Jin - Teal.
 * Kessen II: Once again, Shu's officers dress in Green, but Wei and Wu switched. Wei officers in this game wear Red and Wu's army dress in Blue.
 * In Resonance of Fate, weapons, damage displays, and damage is displayed in either blue or red, depending on if they do Scratch or Direct Damage, respectively.
 * Bio Shock and its sequel color-code the security turrets, bots, and cameras: red ones are hostile and green ones have been hacked to be on your side. The lights on the Big Daddies' suits' portholes are similar: yellow light means it's neutral, green means it's hypnotized, and red means it's hostile.
 * Donkey Kong 64 was practically built around this idea. If anything important pertained to a certain character, one simply had to look at the color to figure out to whom the task belongs. For Donkey Kong, it was yellow; there was red for Diddy, blue for Lanky, purple for Tiny, and green for Chunky.
 * Borderlands: Anything that can be interacted with (chests, switches, quest items) has a green light or aura. Considering Pandora is a barren wasteland, greenery really stands out.
 * Mario & Luigi: Bowser's Inside Story has several bosses and minigames where Mario and Luigi can each only deal with half of the threats--for instance, a scrolling shooter-style minigame where each of the things to be shot can only be shot by a specific brother. Mario and Luigi wear red and green, respectively, so whatever Mario targets is red and whatever Luigi targets is green.
 * Skies of Arcadia has its six oddly colored Moons that also correspond with elements, as well as the continent under it's environment:
 * Green Moon - Nature. Its continent is made mostly of lush, quick-recovering forests.
 * Red Moon - Fire. Its continent is a desert.
 * Purple Moon - Ice. Its continent is a barren land of snow and ice.
 * Blue Moon - Wind and Water. Its continent is often struck by fierce wind and has many watery environments.
 * Yellow Moon - Lightning. Thunderstorms occur every day in its continent.
 * Silver Moon - Life and Death. Nothing notable happens in the world below,
 * In Wario World, the 8 treasure chests and their corresponding buttons are Color Coded for Your Convenience. The 5 colors for the Spritelings also count.
 * The Legend of Zelda Ocarina of Time has certain colors corresponding to Locations, Elements, Races etc. that are all aligned.
 * Green - Forest/Wood (Wind)/Kokiri (Koroks, Deku)/Farore (Courage, Link)
 * Red - Mountain/Fire/Gorons/Din (Power, Ganon)
 * Blue - Lake/Water (Ice)/Zoras/Nayru (Wisdom, Zelda)
 * Orange - Desert/Spirit/Gerudo
 * Purple - Graveyard/Shadow (Earth)/Sheika
 * Yellow - Hyrule/Light/Hylians
 * Guild Wars color-codes just about everything. Professions are color coded, and skills for that profession have icons of predominantly that color, and the bosses of that profession have an aura of that color, and so on. Pv P and the factions in Factions use the classic red vs blue setup. In some Pv P maps, they even color-code the objectives to group them!
 * Inside the main Mass Effect series, the Paragon and Renegage moralities are associated with blue and red, respectively. It is especially shown with endings of the games of the main series, with the colour motif of the chosen morality being displayed in it.
 * In Mass Effect 2, the merc groups are distinguished from one another by their armor color and the races of its members: the Blue Suns have blue armor and are staffed by humans, turians, and batarians; the Blood Pack has red armor and consists of krogan and vorcha; and Eclipse uses yellow armor worn by humans, salarians, and asari.
 * Likewise, the life bars are color-coded: purple for biotic barriers, blue for tech shields, yellow for armor, red for health.
 * In Mass Effect 3, you may get a red, green, or blue
 * In the Wing Commander series, Terran Confederation fighters are generally painted in bright colors, typically silvers and greens for the first two games and bright grey for the remaining (except for the Excalibur and Dragon superfighters, which have dark-colored hulls). Kilrathi fighters are generally ochres and darker colors. And Border Worlds Militia fighters are gunmetal grey.
 * In the Tomba series, Items are split into 3 colors in the select item menu: Green, Blue, and Pink. Green Items are equippable weapons and clothes. Blue items are regular items such as the Buckets and lunch boxes. Pink Items are special automatic use items such as the Evil Pig Bags and the Treasure Chest Keys that can only be used by talking to the right NPC or doing something in the right location.
 * In World of Goo, different species of goo balls have different colour. It'll be difficult to tell them apart without this.
 * In Trauma Center, there is a type of GUILT called Tetarti. It can come in groups of 3 with three, four, or five colors. Their color is shown when they appear and then they turn gray. To kill them, you must inject each one with the serum that has the same color.
 * Pokémon:
 * The three starters of each Gen are Green, Red, and Blue.
 * Pikachu is officially the Yellow of Gen I, but implicitly the Yellow of every Gen because of the Anime, despite how many expies it has.
 * Also, each of the 17 types has a color associated with it:
 * Jade=Bug
 * Black=Dark
 * Indigo=Dragon
 * Yellow=Electric
 * Red=Fighting
 * Orange=Fire
 * Lavender=Flying
 * Purple=Ghost
 * Green=Grass
 * Tan=Ground
 * Cyan=Ice
 * Beige=Normal
 * Magenta=Poison
 * Pink=Psychic
 * Brown=Rock
 * Gray=Steel
 * Blue=Water
 * And each of the version mascots, except in Black and White, matches its version color. For the ones that aren't obvious by the name, Crystal is Purple/Light Blue, Diamond is Baby Blue, Pearl is Pink, and Platinum is Gray Red and Gold.
 * Sonic the Hedgehog:
 * Each of the characters' fur/feather/body color tends to follow them everywhere. An interesting case is Shadow, whose fur is Black with Red highlights: he is usually associated with Blacks and Grays or Dark Red, but for some reason, his attacks are all orange.
 * In the game Sonic Heroes, the twelve playable characters are divided into four teams of three members each. Each team consists of a speed character, a flying character, and a power character. Most obstacles are color-coded to tell the player which team member is intended to clear that obstacle with blue for speed, yellow for flying, and red for power. These colors are based on the fur colors of the "main" team featuring Sonic as the speed member, Tails as the flying member, and Knuckles as the power member.
 * In Bureaucracy, all villains and obstacles will be denoted by whatever you told the game your least favourite colour is.
 * Touhou games have red items for power, blue for score, green for Smart Bombs (except in 10 and 11, where bombs were tied to power, and green items increased the value of blue items), and purple for extra lives.
 * The characters in Team Fortress 2 work for two companies called RED and BLU [sic]. It's no coincidence that the Administrator and her assistant both wear purple. Even with all the unlockable weapons and modifiable accessories, the game has never allowed you to wear the colors of the opposite team (not counting disguised Spies, of course).
 * Dwarf Fortress features dwarves that are different colors depending on their jobs, the result in your main meeting room being a mess of brown, white, grey, blue, etc. smiley faces.
 * Gears of War tends to give the COGs blue lights on their armor and the Locusts red.
 * The Hard version of Rockman No Constancy colors Mega Man green rather than blue.
 * In 50 Cent: Blood on the Sand, ammo pickups are colour-coded based on the weapon type--blue ammo is for close-range weapons, yellow is for machine guns, and red is for special weapons like snipers and rocket launchers. The enemies you fight are also colour-coded in this way to tell you what kind of weapons they're equipped with.
 * Cactus and Mr. Podunkian's game Dungeon uses a simple system for its Retraux graphics. The player, the walls, and all harmless decor are white. Deadly objects and enemies are red.
 * The platform game Star Guard, also with Retraux graphics, uses simple colors as well. You and your allies are green. Deadly things are red.

Web Comic

 * Schlock Mercenary gives us an in-universe example, with Lt Shodan's suspicion that a bunch of new recruits charging ahead and blazing away with their guns were prevented from shooting one another only because they were wearing the same color.
 * Invoked in Adventurers!, where a (probably ice) dragon painted himself red to make the adventurers think he was a fire dragon and thus immune to all their fire weaponry. It worked, and they just gave up.

Web Original

 * In Elcenia, dragons' colors indicate their magical abilities. In addition to breathing fire of their color, reds gets improved firebreathing and fire resistance, greens get magical empathy, blues are better shapeshifters, violets can breathe underwater, blacks get improved senses, and whites fly better.
 * Noted by Tobuscus in his Tron Legacy trailer parody.

Western Animation

 * G.I. Joe - The good guys shot red laser beams and the bad guys shot blue ones. If a good guy picked up a bad guy's weapon and started firing...it would switch colors.
 * The villains of the show "Cheat Commandos" from Homestar Runner are actually named Blue Laser.
 * Towers in Code Lyoko glow different colors depending on who is controlling them at the moment.
 * XANA - Red
 * Jeremie - Green
 * Uncontrolled - Blue
 * - White. Also used for inactive towers on Lyoko in later seasons, which is either a continuity error or Fridge Brilliance.

Real Life

 * The Québec student strikers of 2012 adopted the Red Square as their symbol against the 75% hike in tuition and in favor to the strike. As it gained in popularity both in the student body and the general population, other factions in the conflict tried to promote their own squares, with varied levels of success...
 * Some students wore the Green Square to show support for the hike and taking a stand against the strike;
 * Other students wore the Blue Square, which meant they were against the hike, but were also against the strike;
 * At some point, columnist Richard Martineau suggested the Yellow Square, which meant that you would favor a [i]smaller[/i] hike. It never caught on. In fact, the Yellow Square already had a significance before (though perhaps not publicized enough) as anti-nuclear stand in the province of Québec.
 * As the conflict dragged on, some parents and teacher adopted the White Square, urging both the governement and student unions to compromise with a moratorium on tuition hikes, until such time as we could discuss the matter with cooler heads.
 * When the government passed bill 78, which would restricts freedom of assembly, protest and picketing, especially on or near university grounds, writer Normand Baillargeon suggested the Black Square (to be worn WITH the Red Square) in protest of the violent repression suffered by student strikers since the beginning of the conflict, and as a symbol of grief over the death of democracy.
 * This is quite common for any metropolitan mass transit system that's extensive enough to have multiple lines, although it's a toss-up whether the residents of a particular city call the lines by their colors or their actual names (assuming they have other names; some just pick a colour and use that as the name).
 * The "Hanky Code", a series of signals supposedly used to indicate kink and gender preferences in bars. The color of the hanky indicates the activity and the position of the hanky (left or right back pocket) indicates a dominant or submissive.
 * Many screwdriver or plier sets have the handles color-coded by tool type (for example, all flathead screwdrivers will have yellow handles while all Phillips heads will be blue) so that you can tell what type of tool it is at a glance.
 * The PC99 standard gave us the color-coded ports and plugs we all use today to tell the difference between identical plugs that go into identical sockets with different uses (e.g. headphone and microphone jacks, old PS/2 keyboards and mice, etc.).
 * Similarly, electronic components are color coded so electricians can tell their power and tolerances at a glance.
 * US aircraft carrier flight deck personnel. "Explosive Ordnance Disposal" -- Red. Ouch. As if it didn't sound dangerous already.
 * In Elizabethan England, the actors on stage were color-coded - rather than wear costumes fitting the era/location the play was said to take place in, modern-day outfits of different colors were used to tell whether a person was a ghost, wealthy man, etc. This made it easier for less-educated people to understand what was going on.
 * Pre-Communist political offices were identifiable by color, the pattern on their uniform, and the fanciness of their Nice Hats.
 * Most sports teams have one or two colors associated with their logos/jerseys. In international competitions (World Cup, Olympics), it almost always overlaps with National Colors.
 * In soccer matches, however, this is oftentimes subverted. Italy, for example, plays in all blue, although Italy's National Colors are Green-White-Red. Germany's classic dress is white shirt, black shorts, and white socks, whereas the National Colors are Black-Red-Gold.
 * Many military forces will have particular colors they are associated with (for instance, the Red coats that the British army wore for some time). In modern times, said colors can distinguish between branches of a nation's military or, in some cases, smaller branches within those branches.
 * In 1940, when the risk of a German invasion was at very high, the Irish army switched their uniform color and helmet style (which, at the time, were similar to Germany's) to emulate Britain's, so they would be readily identifiable as allies from a distance by British soldiers.
 * Russians With Rusting Rockets takes it to eleven with colour-coded undershirts. No, seriously. It started back in XVIII century, when sailors traditionally wore striped undershirts (telnyashkas) and so did the naval infantry. Their stripes were either deep-blue or black. Everybody knows that sailors are Badass and marines are even more badass, so when, after World War Two, airborne corps were created, they received light-blue-striped telnyashkas. The first commander of airborne corps, Vasiliy Margelov, was a former marine, you see. Then, around 90's, the idea got around that you cannot be badass if you don't have telnyashka, so various forces started to introduce their own colour schemes.
 * Sailors: Dark blue stripes
 * Naval Infantry: Black stripes
 * Airborne troops (VDV): Light blue stripes
 * Border guards: Green stripes
 * Ministry of Interior (MVD): Red stripes
 * Emergency Control Ministry (Emercom): Orange stripes
 * Soldiers do not wear a striped telnyashka--their undershirts are white.
 * Cigarette packaging tends to follow a general color-coding scheme, although it's far from universal. About the only thing that's consistent across most brands is that if it's in a green or predominently green pack, it's menthol.
 * Red = full flavor
 * gold or blue = lights
 * silver or white = ultra lights
 * green = menthols
 * On military ships, the colors of pipes indicate their contents
 * red = fire main (sprinklers/fire hose)
 * blue = potable water
 * yellow = fuel oil/gasoline
 * green = salt water
 * Artificial flavoring in the U.S. tends to follow a set pattern somewhere between this and Tastes Like Purple for things that are flavored, such as Popsicles, fruit drinks, or candy.
 * Red = Cherry (sometimes Watermelon)
 * Pink = Strawberry
 * Orange = Orange
 * Yellow = Lemon or, less frequently, Banana (occasionally Pineapple)
 * Green = Lime or Mint, very occasionally used for Apple.
 * Blue = Blueberry or Blue Raspberry.
 * Purple = Grape
 * White = Pineapple, Coconut
 * Fruits change colour depending on how ripe they are. This is thought to be why humans evolved colour vision in the first place. Additionally, recent studies have shown that women see far more different shades of color than men (where a man will see "beige," women will see beige, tan, bone, ecru, and several other shades that men don't). They believe this is a holdover from the old caveman days, when women were the gatherers and had to differentiate between "safe to eat" red berries and "highly poisonous" red berries.
 * Dairy products in the US. Whole milk is almost always red. 1% milk is usually dark blue. Half-and-half is usually purple. Chocolate milk is brown.
 * Some types of medication, particularly those that are to be taken on an on-again/off-again schedule like some birth control pills. It's easier for the person to take a pill every day than to try to remember how many days they have already skipped/still need to skip so the meds are packaged with placebos for the skip week; those pills are a different color to the actual pill.
 * Most stars:
 * O-type stars= blue
 * B-type stars= bluish-white
 * A-type stars= white
 * F-type stars= yellowish-white
 * G-type stars= yellow
 * K-type stars= orange
 * M-type stars= red
 * brown dwarfs= maroon
 * neutron stars= purple
 * black holes= black
 * Horse racing:
 * 1= red
 * 2= white
 * 3= blue
 * 4= yellow
 * 5= green
 * 6= black
 * 7= orange
 * 8= pink
 * 9= turquoise
 * 10= purple
 * 11= gray
 * 12= lime
 * 13= brown
 * 14= maroon
 * Some high schools colour code the uniform shirts based on student's ages . See also the Degrassi example above.
 * Many street gangs have one or more colors associated with that particular gang. For example, the Crips are blue and black and the Bloods are red and black. This can lead to hilarity of the deadly type for people who wander into gang territory wearing a rival gang's colors, intentionally or not.
 * International auto racing, prior to The Seventies:
 * Red = Italy
 * Light Blue = France
 * Gray or silver = Germany
 * Dark Green = UK
 * White over Dark Blue = USA
 * Many space-filling or ball-and-stick models of certain molecules will have certain elements given a specific color. Here are some examples:
 * Hydrogen = white
 * Carbon = black
 * Nitrogen = blue
 * Oxygen = red
 * Fluorine = dark green
 * Sulfur = yellow
 * Chlorine = light green
 * One aversion in real life that's still played straight in fiction: Gemstones. While in real life, most gems have the ability to be a variety of colors, in fiction, they still follow a pretty set pattern:
 * Diamonds = Clear/White
 * Emeralds = Green
 * Rubies = Red
 * Sapphires = Blue
 * Topaz = Yellow
 * Amethyst = Purple
 * The "hoods" (more like shawls) worn by college faculty at graduation ceremonies are doubly color-coded: the velvet collar's color indicates either Doctoral status or the wearer's field of study, while the interior fabric displays where the faculty member's own education took place.
 * Electrical components such as resistors and transformers generally follow a (rather complex) color-coding scheme - the more bands it has, in the case of the Resistors, the higher ohms its resistance is, and the individual colors are multipliers for the base number, as seen here.