[[quoteright:329:[[Manga/MermaidMelodyPichiPichiPitch http://static.tvtropes.org/pmwiki/pub/images/tvt_curtainsmatchthewindow.jpg]]]]
[[caption-width-right:329:Blue, purple, green, no hair dye required.]]

->''"And for some reason, I got blue hair. [[TropeNamer You gotta have blue hair.]]"''
-->-- '''Strong Bad''' (describing his {{anime}} counterpart, Stinkoman), ''WebAnimation/HomestarRunner'', [[http://www.homestarrunner.com/sbemail57.html "Japanese cartoon"]]

Though there are plenty of ways to differentiate characters from each other, one of normally limited utility is hair color. Human hair has a limited amount of variation, after all, not enough to make everyone on a half hour show once a week [[ColourCodedForYourConvenience easily distinguished]]. Thus, this {{trope}} was born, so that artists could use the full spectrum of color. It's so common that it's mostly considered an AcceptableBreakFromReality now.

This is especially common in {{anime}}, where characters often have impossible hair colors. This started with {{manga}} series that used distinctive colors on the covers to make characters stand out, even though they all had either dark or light hair in the actual black-and-white pictures; {{anime}} brought it to the screen and [[AdaptationDyeJob made it a standard part of character designs]].

There are several reasons why artists do this. The first, noted above, is to help distinguish characters from each other, as with AnimeHair. It may be done to indicate character personality, such as an EmotionlessGirl [[ReiAyanamiExpy with blue or white hair]]. It may indicate that a character is unique, if they are the only one in the cast with their hair color. Or it may be done just to suit the artist's taste for variety. In some cases, artists may use PowerDyesYourHair to explain how a character gets unusual hair when otherwise trying to be realistic in their hair color choices. Also not uncommon is that the CurtainsMatchTheWindow.

Some specific colors have {{subtrope}}s which ascribe certain character traits to them: such as [[ShyBlueHairedGirl a blue-haired girl being shy]], a [[RoseHairedSweetie pink-haired girl being cheerful or passionate or sweet]] (take your pick), and [[WhiteHairBlackHeart a white-haired young-man being evil]].

A {{subtrope}} of HairColors. HairColorDissonance is when hair is ''depicted'' as an odd color, but is supposed to be a normal color (e.g., powder blue standing in for grey); specifically, when hair of a very dark shade of blue or purple is supposed to represent black hair, that's PurpleIsTheNewBlack. When the hair color is realistic but is not justified by the setting, that's ImplausibleHairColor. For characters with impossible hair ''styles'', see AnimeHair.

See also AmazingTechnicolorPopulation and {{Mukokuseki}}.
* YouGottaHaveBlueHair/{{Anime}}
* YouGottaHaveBlueHair/ComicBooks
* YouGottaHaveBlueHair/FanFic
* YouGottaHaveBlueHair/{{Film}}
* YouGottaHaveBlueHair/{{Literature}}
* YouGottaHaveBlueHair/LiveActionTV
* YouGottaHaveBlueHair/{{Music}}
* YouGottaHaveBlueHair/ProfessionalWrestling
* YouGottaHaveBlueHair/TabletopGames
* YouGottaHaveBlueHair/VideoGames
* YouGottaHaveBlueHair/VisualNovels
* YouGottaHaveBlueHair/WebComics
* YouGottaHaveBlueHair/WebOriginal
* YouGottaHaveBlueHair/WesternAnimation

[[folder:Comic Strips]]
* Used for comedy in ''ComicStrip/TheLockhorns''. While the couple passes a woman literal blue hair, Leroy mutters "Remember when [[ElderlyBlueHairedLady blue hair meant being old]]?".

* In ''Pinball/BanzaiRun'', Blue Beard's hair is a ''very'' light electric blue.
* Annie from ''Pinball/AsteroidAnnieAndTheAliens'' has green hair for some unspecified reason.

[[folder:Web Animation]]
* The {{Trope Namer|s}}, ''WebAnimation/HomestarRunner'', spoofs this when a fan named James [[http://homestarrunner.com/sbemail57.html asks]] what Strong Bad would look like as an anime character. Strong Bad decides that he'd be shiny and have huge green eyes, cooler boots, and blue hair ([[TropeNamers "You gotta have blue hair."]]), for some reason. Humourously, on one [[http://www.homestarrunner.com/main17.html main page,]] scrolling over "Store" gives 1-Up (Homestar Runner's anime counterpart) blue hair.
* ''WebAnimation/AcedemySugoiSeiun'' has characters with bright pink, blue, yellow/orange/red (at the same time), and purple hair.
* Eddsworld had Laurel, a one-time character in the "MovieMakers" episode.

[[folder:Real Life]]
* The celebrated "Glowing Green Monkeys", who were created by gene-splicing lab monkeys with bioluminescent sea creatures. Their hair only glows under fluorescent light, however, and look more of a dull greenish-brown under normal conditions. Bioluminescent pigs, on the other hand, are [[http://gizmodo.com/these-pigs-glow-in-the-dark-to-save-lives-1491589459 bright yellow]].
* A potential result of overexposure to cobalt or indigo dyes during industrial processes.
* Purple squirrels have been showing up around the world. Whether or not it's some sort of prank is unknown. Maybe it's a [[http://en.wikipedia.org/wiki/Purple_squirrel commentary on the job market]].
* Can be invoked using hair dye.