Chameleon Camouflage

Just a thin line above true Invisibility, a character simply fades from sight by taking on the appearance (color and pattern) of the background behind them. Generally done by characters of supernatural leanings, but doesn't require actual possession of invisibility (cloak or otherwise).

See also Wallpaper Camouflage. Related to Visible Invisibility.

Worth noting that chameleons can't actually do this.

Examples of Chameleon Camouflage include:

Anime and Manga

In the various Ghost in the Shell incarnations this is known as thermoptic camouflage, presumably because it also works in infrared.
Teana's Optic Hide spell in Magical Girl Lyrical Nanoha Striker S works this way.
In One Piece the minor villain Zeo is a carpet shark fishman, and can change his color to blend with the ground and apparently disappear. Played for Laughs when he gets stomped and clubbed by his own men.
Dagomon from Digimon Xros Wars: The Young Hunters Leaping Through Time

Comic Books

British comic Cor!! once featured a two-page strip titled "Kid Chameleon". The title character was raised by lizards (!) in the Kalahari (with a little help from some local Bushmen), and wore a suit of chameleon scales to camouflage himself. Don't ask how he did it, but the background colours were allowed to show through his outline.

Film

Played for laughs in Toys. Patrick is usually introduced to a scene dressed exactly like some part of the scenery.
Predator: The Predator's camouflage armor worked this way.
Caesar's spy in the animated version of Asterix and Cleopatra. He can even shapeshift into building stones or other scenery elements.
G.I. Joe: The Rise of Cobra: The Joe's stealth suit.

Literature

Being raised by ghosts, Bod does it very well in The Graveyard Book.
From Discworld, Susan Sto Helit, Granny Weatherwax and her apprentice Tiffany Aching have powers to do this. The young Vetinari learns this in Night Watch (to the point that he nearly fails his Camouflage class for nonattendance), and Vimes has an uncanny ability to blend neatly into shadows.
Harry Potter: The Dissillusionment Charm has this effect, and if done well enough can confer actual invisibility. Putting it on a garment is one way to make an Invisibility Cloak, though the charm fades over time.
The Sword of Truth has mriswith, lizard people capable of changing their color for a fairly good concealment. They also wear capes which do the same, but much better.
In Hyperion, military Power Armor works that way.
In the Redwall novel Marlfox, this is the ability that marks the eponymous Marlfoxes.
Deconstructed in Beetle in the Anthill, when Abalkin explores a deserted planet, equipped with a suit that is supposed to give him whole-body Chameleon Camouflage. However, it malfunctions and doesn't actually do anything, so Abalkin takes off his helm for better vision. Then, just as he encounters the local Human Aliens, the suit suddenly powers up and presents him as a floating head, scaring the shit out of the locals (to the point where they open fire).
In Cryptid: The Sleestaks, as well as several other cryptids.

Live-Action TV

Zhaan did this in an episode of Farscape when she turned invisible by blending with other foliage (she's a plant).
Eugene Bryant in the Fringe episode "Wallflower" has this ability, since he's been genetically modified to shift his pigment around like an octopus.
One episode of The Avengers had a villain escape prison and attempt to murder John Steed with such a gimmick.
A natural ability of Nestov and other Dessarians on Tracker. They can both blend into any enviroment in a more general sense and literally disappear into the background of it.

Tabletop Games

Dark Conspiracy supplement Darktek. The alien ET's had a Chameleon Suit which changed its colors to match the background.
Shadowrun supplement Shadowtech. A chemical compound called ruthenium polymers could be used to change something's color (e.g. a stealth suit or vehicle) to match what was behind it, allowing it to blend in and disappear.
Dungeons and Dragons
- The 1st Edition Fiend Folio introduced the Skulk, a humanoid creature whose camouflage ability allowed them to blend into any background. They used this ability to sneak around stealing and murdering. Bullywugs (frog-people) had chameleonic ability (75% undetectable in natural surroundings, penalty to the opponents' surprise roll), Pseudodragons did it even better.
- The Cloak of Elvenkind had chameleon-like abilities, allowing the wearer to be almost invisible in natural surroundings. The Ring of Chameleon Power, Potion of Blending, and in AD&D2 Chameleon Cloak had similar effects.
- Classic (D&D - AD&D2) psionic powers include "Chameleon Power".
Iron Crown Enterprises' Cyberspace RPG. The C-Cloth (Chameleon Cloth) coverall could change colors to match its surroundings.
The Hollow Earth Expedition supplement Secrets of the Surface World had a Chameleon Suit as a possible Weird Science gadget.
Gamma World. The Chameleon Powers mutation allowed its user to change its colors and blend into the surroundings.
The Mutant Future RPG (which ripped off its list of mutations from Gamma World) had the Chameleon Epidermis mutation that worked the same way.
Terran Trade Authority RPG. The Camo Suit scanned the area around it and replicated it on the surface of the suit, causing it to blend into the surroundings. This rendered the wearer almost invisible in low light situations and partially camouflaged even in bright light.
Warhammer 40,000 has Cameleoline - material changing coloration to match the surrounding, used for coating wargear - mostly as universal camouflage cloaks.

Video Games

In Bloody Roar 3 and Primal Fury, Busuzima's beast form is that of a chameleon, which allows him to blend in with the arena; effectively making him invisible.
The Elder Scrolls games have "Chameleon" spells, enchantments, and potions that do this.
Metal Gear Solid 4: Guns of the Patriots features the OctoCamo suit worn by Snake, named after the octopus and designed to mimic its natural camouflage skills. With it, Snake can change the color and texture of his suit to match whatever he's pressed against in a matter of seconds. Later in the game this is partnered with FaceCamo, which normally looks like a sock draped over the wearer's head, but can also make a flawless disguise by mimicking someone else's face.
- In Metal Gear Solid 3: Snake Eater, it's possible to kill The End during his introductory cinema. If you chose not to kill him, you'll have to track him across three massive areas using infared vision since he can seamlessly blend in with the surrounding forest.
From the Mortal Kombat series, Reptile, who has this as a special in several games, and as his intro stance in 9. His introduction in 9's Story Mode is also done this way. Strangely, Khameleon and Chameleon, the bonus characters of Mortal Kombat 3 and Mortal Kombat Armageddon, doesn't have this power.
The Camouflage bonus adrenaline combo in Unreal Tournament 2004 allows the user to become a piece of the level he's playing.
In the Sonic the Hedgehog series, Espio the Chameleon has this ability, and in Sonic Heroes, it's required to pass certain stages.
In the Warcraft universe, Night Elves can Shadowmeld, allowing them to turn invisible as long as they don't move by merging into the shadows. Also in World of Warcraft, rogues, druids and hunters all have some kind of stealth or camouflage ability that allows them to fuse with their surroundings and be partially or totally invisible.
The Stealth Parasites can do this in Evolva.
The cloaking devices in Starsiege, when active, painted your mech the same color as the background terrain (which you could verify with the third-person camera).
Pokémon: Kecleon, a chameleon Mon, has this ability, as well as any Pokemon that can learn the move Camouflage (in game it changes the type of the user to match the terrain, but in the anime and other adaptations it's used as this trope).

Web Original

Red vs. Blue: Agent Carolina's armor ability, where she can instantly change her armor's color to anything she needs.

Western Animation

In The Simpsons episode "Lemon of Troy", Milhouse has an Imagine Spot that while wearing camouflage he blends into the bushes completely.
In Monsters, Inc., Randall is able to do this.
Zartan from G.I. Joe has this ability in addition to being a master of disguise. It came at a cost though using the ability caused him to develop a painful skin condition. In the comics, he eventually found a medicinal cure but had to keep taking it regularly.
How to Train Your Dragon: According to the "Book of Dragons", the Change-wing can use its colorful scales to disappear into any environment.

Real Life

Several species of octopus do this both to hunt prey and to hide from predators.