Taste the Rainbow

This trope describes when a particular element of a story or setting has been expanded to the point that there's a version to suit every viewer's preference. Another way to describe it might be "a taste for every appetite".

Sometimes this happens gradually, over the course of a series/setting - usually in response to fan demand or just because it's good marketing. In some cases it grows into a Plot Tumor proper.

A codifying example would be the Elf as portrayed in the Dungeons and Dragons tabletop roleplaying game, where the basic "Elf" player race found in the Player's Handbook quickly branches into Dark Elves and Wood Elves in the Monster Manual/Dungeon Master's Guide, and in other official sourcebooks includes Gold, Grey, Sun, Moon, Wild, Sea, High, infernal and celestial variants, Half-Elves and Avariel, just to name a few. Third-party books include countless further versions.

This trope is tied to most "Our x are different" Tropes, but isn't quite the same; this trope denotes the explosion of "difference" in a single series or setting, rather than just the varied interpretations of an idea between settings. The Cast Full of Pretty Boys and Fundamentally Female Cast can also be examples of this trope, since they generally exist to provide a large cast catering to a number of niche archetypes and fetishes/paraphilias.

The vast selection of deities in most polytheistic religions is a real-life Ur Example of this trope.

Romance Games do this all the time. For Otome Games and Boys Love Games, there's a standard cast: The rich guy, the energetic, straightforward guy, the cool, aloof guy with glasses, the athletic guy, the guy who is pretty as a girl, the "cool older brother" type, and the suspiciously young-looking guy.

In a case where the setting Tastes The Rainbow on a cosmological level, it's probably a Fantasy Kitchen Sink where All Myths Are True.

The title comes from the advertising slogan for Skittles candy.

Anime and Manga

 * Gakuen Heaven is a Boys Love series set at an exclusive high school that includes every archetype of guy there is - and all of them are hot!!
 * Negi's class in Negima is a walking Taste the Rainbow, covering almost every imaginable female character trope appreciated in anime, and at least suggesting most of the fetishes. If we extend the range beyond the class itself, we hit pretty much every conceivable form of Fetish Fuel at some point. As well dozens of iterations of Rule of Cool.
 * The entire point of the Ouran High School Host Club (the titular club, not the series itself) is to cram in as many different forms of female-aimed Fan Service and types of hot guy as possible.
 * Martial arts in Ranma ½ fit this trope perfectly. No matter what hobby, lifestyle or animal you can imagine - from flower-arranging to breaking and entering - somebody in the Ranma universe has made it into a martial art.
 * The World Only God Knows makes sure to include every single female archetype found in a Romance Game -- with a few curveballs to make the Genre Savvy protagonist's life harder.
 * Saint Beast has bishonen of every shape, size, Character Alignment, archetypal personality, and shipping potential a fangirl could want. And they probably do cover the entire rainbow as far as hair colour goes.
 * The class in Sayonara, Zetsubou-sensei is like Negi's, but with severe personality disorders instead of fetishes (well, they're prolly someone's fetishes...).
 * Queen's Blade. If it's a Fetish Fuel, it's represented with a character in its universe. Examples include Lesbian Vampire Maid, Yandere Catgirl warrior, and an Action Mom who can use her own huge tract of land as makeshift pillows.
 * The Idolmaster - Same as the game.

Literature

 * Polytheism is parodied in the Discworld, where there is a god for just about every niche you can imagine (Anoia, the Goddess of Things That Get Stuck in Drawers, is probably the most commonly-seen example).
 * The list for The Dresden Files isn't quite as numerous as some of the other examples, but Harry has faced off against three highly varied species of vampires, with another species mentioned offhand (thankfully, none of them sparkle). There's also just about any variation of faerie you can imagine (along with more than a few you'd rather not).
 * Werewolves, too. Most of a chapter of the second book is devoted to explaining the differences between the various types.

Film

 * Fighting robots in Real Steel show a tremendous amount of variation apart from their humanoid shape.

Live Action TV

 * Power Rangers - ignoring the multicolored spandex jokes - has a team for just about anything that falls under the Rule of Cool: dinosaur Rangers, ninja Rangers, car Rangers, beast Rangers, wizard Rangers, and so on and so on...
 * Depending on how things will turn out, we may get pirate Rangers in a near future.

Tabletop Games

 * As above, the Dungeons and Dragons RPG illustrates this trope beautifully with elves, and occasionally dwarves (though the dwarves tend to have very little actual variety).
 * If elves are the best D&D example, dragons are certainly second. Chromatic (evil-aligned) and metallic (good-aligned) groups reside in the core books, along with not-quite-dragons like pseudodragons, drakes and fairy dragons, while later expansions introduce the various gem (psionic/neutral-aligned) varieties, shadow, fang, force, prismatic, sand, pyroclastic, stygian, and various oriental versions (once again, just to name a few). Of course, dragons also seem to breed with anything that moves, meaning there are also countless "draconic" versions of other critters as well. There truly is a dragon for every season.
 * That is, every season on every planet in the multiverse, not just 4.
 * It was a joke for a while among the Exalted developers that the only perversion that didn't exist in Creation was Pyrohomonecropedobestiality: "Having sex with a dead underaged animal of the same gender that's on fire".
 * Much to the dismay of the god of having sex with a dead underaged animal of the same gender that's on fire, who is the only god in Creation who has been out of work for his entire existence as a result. Creation kind of operates on a modified version of Rule 34: if it exists, there's a god for it. No exceptions.
 * I'm sure that by now, some GM has included pyrohomonecropedobestiality in his campaign.
 * Clans and Bloodlines in Vampire: The Masquerade eventually became this.
 * In Warhammer 40000, there's a space marine faction for whatever particular flavour you like. The same is true of Imperial Guard, where every guard faction is an expy of a real-world military stereotype, complete with a faction who define themselves by surrendering.
 * Japanese Romance Games do this all the time. Now imagine if every single beautiful woman from every single Eroges duke it out in a card game. That would be the general feeling of Lycee TCG. Characters that share archetype also share "colors" and Standard abilities, but each character has her (or his ) unique Character ability.

Video Games

 * Touhou. It's doing it's best to include an Fundamentally Female Cast version of just about everything from Japanese folklore. The earlier games include some western creatures as well.
 * The Harvest Moon series is playing into this more and more each generation with their bachelors and bachelorettes. There's almost always a Girl Next Door, a Strange Girl, a Tsundere, et cetera, et cetera.
 * The Idolmaster uses this as premise for including in the cast every possible Moe archetype.

Western Animation
"Lauren Faust: There are lots of different ways to be a girl. You can be sweet and shy, or bold and physical. You can be silly and friendly, or reserved and studious. You can be strong and hard working, or artistic and beautiful. This show is wonderfully free of “token girl” syndrome, so there is no pressure to shove all the ideals of what we want our daughters to be into one package."
 * Total Drama Island - 22 contestants (with added 13), each one more different than the other.
 * Lauren Faust has explicitely stated that she has designed the Mane 6 characters in My Little Pony Friendship Is Magic to cover all the different personalities of girls.