A list of anime and manga where you can find unnatural hair colors.
At any rate, a list of anime not using this trope would be shorter.
In Ai Yori Aoshi, secondary characters have realistic hair coloring, but most of the lead characters don't. Kaoru's is brown (a very non-Japanese brown), Aoi's is (appropriately) blue, Taeko's is a reddish-brown, Miyabi's is a plum color, and Mayu's is bright purple.
In ARIA, most everyone has normal colored hair, except for some of the main characters; Akari's hair is pink, Alice has green hair, and Athena's hair is lavender.
Chirico from Armored Trooper VOTOMS has blue hair, along with a few other minor characters. Most of the other major characters have normal hair colors, though.
Banner of the Stars has a race of blue-haired space elves. Considering that the Abh were genetically modified to be able to live in space, to the point of having crafted a sixth sense for flying spaceships, the hair colour is really the smallest oddity...
CielPhantomhive of Black Butler has darkish blue hair in the anime. Slightly odd given that, in the manga, it's dark grey in colour shots, only occasionally rendered as blue. Soma's hair was always purple, though. (...until that one time it was rendered as brown, coincidentally on a cover where Ciel's hair looks bluer than usual.) Madame Red and GrelleSutcliffe both have cherry-red hair, but it's treated like ordinary ginger.
Black Cat is pretty good about using normal hair colors for the most part, with a couple exceptions. Jenos' and Leon's dark green could be easily taken as stylized black, but Rinslet's bright purple and Sven's green stand out.
Bleach runs the entire range from natural hair types, to implausible hair types to impossible hair types. The impossible hair types include:
The anime series Captain Future, based on Sci-Fi novels by science fiction writer Edmond Hamilton, created in Japan in 1978 and famous in Europe during the 1980s, featured at least one main character with blue hair and blue moustache (an older male character).
In Code Geass, the Japanese characters tend to have realistic brown or black hair, while the Brittanian characters have somewhat more outlandish hair colors and styles. C.C.'s green hair is apparently natural, too.
There's also Mao and the Chinese Federation Empress Tianzi. Tianzi appears to be albino, complete with red eyes. Mao may be another example of albinism, as well. Possible, when you consider that, whenever his eyes are shown, they are always "geassed".
Most characters of Chuunibyou Demo Koi ga Shitai! have natural hair colours—Rikka's black can be seen as a stylized black. The lone exception is the light novel-exclusive Satone, who has bright pink hair.
CLANNAD plays this weirdly: the cast runs the gamut of rainbow hair colors...except for Sunohara, whose blonde hair is dyed and is stated to be "an impossible color" (his actual hair color is gray-blue). So...why exactly is that one shade of color impossible when none of the others are?
The other colors (except the Fujibayashi's lavender hair) are similar to black and brown, which are the main colors of Japanese hair. So it can be seen as an equivalent to that. Sunohara is full Japanese and can't have blond hair naturally. Not that it sounds any less weird.
The main cast of La Corda d'Oro contains a rainbow of unnatural hair colors. Let's see...Kahoko Hino's bright red, Len Tsukimori's blue, Ryoutarou Tsuchiura and Kazuki Hihara's varying shades of green, Azuma Yunoki's purple, Shoko Fuyuumi's bluish-green, Kanazawa-sensei's reddish purple, Shinobu Ousaki's the other shade of red, and Keiichi Shimizu's blonde. Lili is a subversion, since he's a fairy and it seems that he came with Seisou Academy's founder from Europe anyway.
Corrector Yui falls somewhere in between this and implausible. In the anime, Haruna has normal roan red hair, while Yui, being blonde, puts it at least at implausible. The other Correctors have rainbow hair, but they're computer programs. In the manga, though, Haruna has unmistakably purple hair, and in the second season of the anime, purple-haired Ai comes in from the real world.
I do, sir. I sure do. But changing the subject, in the anime, Ai's hair can pass as black, while in manga, it's dark purple (in the pilots, it's a greyish brown).
Cowboy Bebop has realistic-looking characters, so the vast majority of them fall under plausible hair colors...except for green-haired Spike, purple-haired Faye, and white-haired, black-hearted Vicious. No explanation given for these unusual hair colors and nobody notices.
As far as Spike and Faye, they're more than likely black-haired with highlights/contrast shades added in.
Clark Kenting related example — everyone in the world of Yes! Precure 5 has some shade of brown or black hair, except for the heroines, all of whom have hair in their respective hero colors even in civilian form. Red-haired Rin and (justified) blonde Urara might not stand out, but Nozomi, Komachi, and Karen's pink, blue, and green, coupled with the fact that the five spend a lot of time together...
Rin's got realistic-looking brown "red" hair, which becomes bright red when she transforms. So maybe that throws people off.
In the Cyborg009 movie Legend of the Super Galaxy, Albert Heinrich (Cyborg 004) has blue hair. In other adaptations, his hair is gray, brown, or bluish-grey.
In a cast consisting of characters that mostly have "normal" hair colors, Death Note's Near happens to have stark white hair, while Matt sports unnaturally green hair, at least, in the anime adaptation and TCG (in the DS game adaptation, it became blue). Some images of L and Teru Mikami also have their jet-black hair mutated to more of a deep black-green, and the very first colored manga image featuring Mello depicted him with hair just as white as Near's.
Diebuster has this in the form of protagonist Nono, whose hair starts out pink and turns into a glowing psychedelic swirl when she regains her memories and recombines with the solar system's dormant defense robot network. Given that this series is from GAINAX, makers of such refined weirdness as Abenobashi Mahou Shoutengai and FLCL, this is probably unsurprising.
Arale in Dr. Slump gets away with this because she's an android.
Dragon Ball has Bulma with blue hair. Trunks gets his purple hair from his grandfather and it turns gold when he's Super Saiyan.
In the manga, her hair is also purple, as well as Bulla's. They could have also changed Trunks' for consistency, but noooo...
Also, in the anime, as opposed to the manga, Launch (when not in her gun-toting form, where she's a blonde) doesn't have black hair with blue tones, but dark blue hair instead, almost like the print media example.
The opposite applies to Chichi, whose hair is regular black in the anime and blue-black in the manga. It seems like Akira Toriyama probably planned her to have, indeed, dark blue hair, but colored it black in the manga to save reticulum patterns (since her hair would be so dark it would be unnecessary), not the other way around.
Dirty Pair fall into this: Kei is a Dark-Skinned Redhead with an impossible shade of red hair, and Yuri's hair (even when it's referred to as black) is usually shown as blue. However, they are both genetically engineered transhumans with a questionable biology/cybernetics ratio.
The spinoff Dirty Pair Flash takes it even farther, with Kei having two-tone orange and blonde, and Yuri's hair being lavender.
All members of the Diclonius sub-species in Elfen Lied have hair in varying shades of pink (in the anime, at least). Justified in that they are not entirely human. Also, their hair color, combined with the cat-ear-like horns on their head, single them out among crowds of humans. Quite unusual for a manga, all the regular humans actually have realistic hair colors, and only the Diclonii live up to this trope. Only stand-out among the regular humans is Yuka who has straw blond hair, but is Japanese. However, we never see her parents, so she might have some Caucasian blood running in her family.
In the manga, the "third-generation" Silpelit, Mariko, has blond hair, which is completely impossible considering the fact that her parents were both Japanese and had dark hair.
In Fairy Tail, the main hero, Natsu, has pink hair. One of his companions, Erza, is a red-head (not orange-red, cherry-red). Erza's antagonist character (since every character has one big bad affiliated with them), Jellal, has blue hair.
Erza's surname, "Scarlet", was actually given to her because of her hair color.
Mirajane in all her white-haired beauty.
Mirajane's siblings, Rob, Brain/Zero, and Angel have white hair as well.
Happy is a BLUE ANTHROPOMORPHIC CAT with wings that can fly.
A few other characters as well - Levy, Juvia, and Yuka Suzuki also have blue hair. The former Element 4 had odd hair colors: the aforementioned Juvia, Totomaru had white and black hair, and Sol had green hair.
Porlyusica, Sherry, and Ikaruga have pink hair.
Lyon has pale-blue hair.
Bisca and Freed have green hair.
Bickslow has black and blue hair.
Laki and Kinana have purple hair.
The funny thing about The Familiar of Zero is that while everyone in Halkeginia has hair from somewhere of the colour circle, no one except those of Japanese descent have black hair, like Saito and Siesta.
Full Metal Panic! is mostly realistic, but Kaname has blue hair (often described as black), and the Testarossa siblings are white-haired (often described as ash-blonde). Apparently, no-one finds this strange.
All the people that seem to have issues with this in FMP are Whispereds, and all sorts of nonsense can be attributed to this.
In Full Metal Panic? Fumoffu, unnatural hair colors are given out like candy on Halloween. As you may have guessed, it's not so serious.
And then there are the manga covers, which give Sousuke either lavender or light blue hair for some reason.
Tamahome and Chichiri from Fushigi Yuugi have blue hair of different shades (but the former's hair is often mistaken for green), while Nuriko, his deceased little sister Kourin, and Empress Houki have purple hair. Chiriko's hair is a cross between brown and pink and the Nyan-Nyans have bubblegum blue hair. Tokaki, Subaru, and Tenkou have silver hair (this holds true for the former two even in youth), and Renhou and Miiru have silver-purple hair. Soi's hair is a shade of maroon, while Nakago is the only one who has blonde hair in the book world, and this is actually significant. The human forms of all the Beast Deities have hair in the color by which they are identified.
In GA Geijutsuka Art Design Class, while some characters have acceptable hair colours—Professor is black and Kisaragi is deep brown), Tomokane is green, Nodamiki is pinkish-blond, and Namiko is a light brown. Lampshaded in one strip wondering why Western Animation uses Amazing Technicolor Population and anime uses this. These are the characters' in-universe hair colours; Namiko and Nodamiki had to submit their child photos to the school to prove they had not dyed their hair.
For the most part, the hair color choices in Gakuen Babysitters are normal. However, if the official color art is to be believed, Ryuuichi has dark-redish hair, Taka's is blue, and Usaida's is... magenta. Huh.
Tazusa from Ginban Kaleidoscope has purple hair, her best friend's is green, and her rival's is dark red. Pete's dirty blonde hair is justified since he's Canadian.
Many of Gintama's cast members have reasonably realistic hair colors, but Gintoki's silver hair (which somehow appears light blue) sticks out like a sore thumb; this is actually pointed out within the series itself. Then there's Sacchan and Otsuu's purple hair, and Kagura's bright red-orange 'do (though this may be slightly justified in that she's not human.)
GaoGaiGar is somewhat...inconsistent about this. A hair color is normal, or at least unworthy of comment, if it does not come from alien heritage. (Hyuuma could actually have green hair, but it's almost certainly dyed, if so. And Akane probably actually has black hair.) But, Kaidou with red hair apparently looks much stranger than Kaidou with mauve hair. And Kaidou with mauve hair and Hana with pink hair are just as plausible as nearly everybody else's normal hair.
Gundam SEED very carefully and deliberately averted this trope by giving unusual hair and eye colors ONLY to Coordinators, genetically engineered humans, while Naturals, those without genetic modification, had only natural hair and eye colors. The sequel, Gundam Seed Destiny, almost immediately screwed this up with Sting and Auel, Naturals with green and blue hair respectively.
Auel and Sting weren't the first Naturals to have unusual hair colours. Shani, one of the prototype Extended from Seed, had green hair. And there's nothing normal about he or Sting and Auel, what with their being drug-addicted Super Soldiers raised from birth to be living weapons. The only non-Coordinator, non-Extended to have an odd hair colour is Yuna Roma Seiran. And given some of his other, unusual style choices, that's hardly surprising.
Used as a plot point in the spinoff manga Gundam Seed Astray: the mercenary Kaite Madigan is a Coordinator whose parents abandoned him because, due to a genetic defect, his facial hair is a different color from the hair on his head.
Gundam 00 seems to also have done this, where the only people with oddly colored hair (light/dark purple, pastel green, blue) are genetically-engineered Innovators and Ribbons' children, the Trinities, or experimentally modified Super Soldiers, making them easy to spot from a mile away. Having rather odd names (by Real Life standards) also does a good job of spotlighting them.
Both of the Super Soldiers actually have fairly normal hair-colors. Allelujah's is a very dark green, which could just be because it'd be too hard to see if it was completely black, and Soma's is light gray.
Feldt, a normal human, has bubble-gum pink hair, but it turns out she dyes it out of a complex from having been raised in space unlike other people.
Played completely straight in Gundam Age. Besides Flit Asuno having green hair, there are countless hair colors ranging from normal colors like brown and grey to unusual colors like purple and sky blue. Two characters, Ract, the leader of Euba, and Yark Dore, the Disc One Final Boss, even have two hair colors (blonde/red for Ract and blue/gold for Yark).
Mobile Fighter G Gundam averts this trope a good deal, with the only notable exception being Allenby Beardsly, who has sea-green hair. Apparently, in the future, the Swedish will all have this color of hair; one of her workers also has green hair.
The Harukanaru Toki No Naka De franchise is fond of this. Normally, if a character is blond (and has blue eyes), you can tell that said character is really blond and blue-eyed, which indicates that he either belongs to the Oni Clan if he is from Kyou or is not entirely of Japanese origin. The fact that the rest of the central cast makes up a nice rainbow when standing together (the anime adaptations enjoy the effect) doesn't bother anyone, and if you ignore certain characters who aren't quite human, it won't help anyway.
Specifically, among said non-human characters are two green-haired Artificial HumanOnmyoji and a boy with white hair who happens to be a depowered form of a white dragon-like deity, and none of them gets much commentary regarding their hair — as opposed to blond characters.
In Hidamari Sketch, Sae and her anime-only sister have cobalt blue hair. Natsume has green hair. Yoshinoya-sensei and new first-year Nori have green/blue hair. The remaining characters, even the important ones, have regular hair colors.
Atori and Shinji from Hiiro No Kakera both have purple hair. Meanwhile, Oomi has green hair.
Higurashi no Naku Koro ni falls victim to this. Keiichi and Tomitake's hair is brown, unusual for a full Japanese person, while Satoko, her immediate family, and Takano are all blonds (more unusual). Rena and Irie has orange hair (very unlikely for Rena, considering neither of her parents do), Rika and Chie have blue hair for no adequately explored reason, and the Sonozaki family women have green hair. Naturally, no one ever comments on any of this.
Actually, Rena's mom has red hair too.
Rika's hair seems to change color after the first season (not entirely sure if it has to do with the lighting of the scene, or what). It looks like it switches from blue to aquamarine to purple throughout the series, as well as in artwork, figurines, etc.
In Umineko no Naku Koro ni, Bernkastel's blue/purplish hair stands out when compared to the rest of the cast introduced up to that point (she is a magical being: namely, an amalgamation of all the Higurashi's Rika who didn't survive the "Groundhog Day" Loop). It stretches a bit on the very redheaded Battler and white-haired Kyrie (being Japanese), but at least they are natural hair colors.
In Kanojo ga Flag o Oraretara, few characters have ordinary hair colours. Even some of the ones that do have normal hair colours have hair that's unusually bright:
Kikuno has bright lime-green hair.
Kuromiko has purple hair.
Rin has forest-green hair (when it's not stylised as black).
Mimori has dark purple hair.
Tsumugi has light pinkish-purple hair.
Rokudo Mukuro of Katekyo Hitman Reborn! actually does have blue hair, in a sort of "pineapple" hairstyle that has been made fun of extensively by the fans and the author. Chrome Dokuro, the girl Mukuro saves/gives organs to/possesses/protects/etc. has purple hair in the same hairstyle. Semi-minor antagonist Nosaru also has purple hair. And at least three perfectly healthy, youthful characters have white hair (and one has gray).
Subverted/deconstructed in Kemono no Souja Erin, as while Erin and her mother both have (impossibly) naturally green hair, other people notice, and it marks them as part of a village associated with black magic and general creepiness.
The Legend of Sun Knight: the Storm Knight must have blue hair, since the first one had blue hair. Every Storm Knight after him has had to apply blue hair dye every day as part of his role, and 8 out of every 10 has died from kidney failure due to too much hair dye.
Almost no one has normal colored hair in Lucky Star. It's lampshaded when Miyuki (who has pink hair) explains to Konata (blue), Tsukasa, and Kagami (both purple) why exposure to sunlight and seawater changes hair color. Most, if not all, characters with funky hair colors also have that as their eye color. As such, one may pretend that their hair is perceived in their world as being black/dark brown.
This is completely ignored and lampshaded further in the dub, where Konata comments that Miyuki is like her mother "down to the last pink hair."
And, also in the dub, Misao (who actually has brown hair) calls Konata "Shorty McBlueHair" at one point when she asks if that's who wants to borrow the game Kagami is asking her to return.
In the case of Ranka and Mylene, this is probably justified, as it seems to be the case that odd hair colors are a natural Zentradi trait, and both of them have partial Zentradi ancestry; in fact, Ranka has inherited a rare Zentradi trait of naturally empathetic hair, so imagining that green is her natural hair color is hardly a stretch. Milia from the original Macross (Mylene's mother) and Clan Clang from Macross Frontier, both fully Zentradi, have green and blue hair, respectively. The odd ones are Alto, Nanase, and Grace from Macross Frontier; the latter's hair is blue, and the former two have purple hair. Zentradi ancestry seems fairly unlikely in all three cases.
Subverted because they're aliens, but the non-Earthlings from Magical Girl Lyrical Nanoha have some pretty wild hair colors, such as Signum and Caro's pink and the Nakajima family's blue. (Then again, you have to question how nobody picked up on the little girl in the wheel chair wandering around with a bunch of rainbow-haired foreigners in A's.) On the other hand, Nanoha's friend Suzuka is pure-blooded Japanese, and her entire family has purple hair. (Interestingly, that includes the maids, who aren't related to them as far as I know.) Nanoha's friend Alisa's blonde hair is an aversion, though — she's not Japanese.
Magic Knight Rayearth: Hikaru's hair is unnaturally red and Umi's is blue. Various other odd hair colors pop up as well, but as Cephiro isn't Japan (or anywhere else on Earth), this is Justified.
Normal hair colors are almost unheard of in Mahoraba, unless you're male, that is.
In the manga, Kaede has sandy blonde hair, and Ayaka Yukihiro has golden blond hair.
Someone at one point says that Ayaka being good at English doesn't count, since she's only 'half', a claim which offends her and she denies.
Evangeline speculates in the manga that Setsuna probably has white hair and red eyes, but dyes her hair and wears contacts. We have never actually seen this in any of the different versions of the series, though.
Ako has bluish white hair, and Chisame has either green or bright orange hair, depending on if it's the anime or manga.
Only two of the major characters in Mai Hi ME have anything resembling normal hair colors for a show set in Middle of Nowhere Town, Japan — Yukino (brown) and Mikoto (black, with pigtails and gold eyes). Naturally, there's also a blue-haired character in the mix, Miyu — but she's an android, so she has an excuse.
Natsuki may also qualify as having "normal" hair — it's dark blue in the anime, but the supplemental materials describe it as being black, so she most likely simply falls under "stylized black hair".
On the cover of the manga's second volume, Natsuki is shown with black hair.
Marginal Prince features characters with every hair color one can imagine. For starters, the main character Joshua is green-haired and his friend Henri sports blue hair, while Sylvain's is bright pink. In fact, every character has a different, mostly really bright hair color, and with the exception of Mikhail and Ivy (who are both blonde, but not related) none is seen twice among the group of important characters.
The page picture comes from Mermaid Melody Pichi Pichi Pitch, where, for the mermaids at least (except for the Pink ones), hair color also indicates race. Humans and other characters (and Pink mermaids) can have any color.
Minami Juuji of Nabarino Ou has inexplicable green-blue hair. Raikou's pink 'do is okay, since he obviously dyes it (though he, his sister, his mother, and Yukimi Kazuhiko and Kazuho are all natural Japanese blondes). Aizawa Kouichi and Kuro'okano Shijima both have pure white hair, but this is because they're both immortal beings - humans fused with a snowy owl and a white cat, respectively.
Naruto has Sakura, who has pink hair (and Theme Naming based upon her hair colour). And it's apparently natural, unless she's going to the trouble of dying her eyebrows. If not for her, it would fit possibly into plausible hair due to the show not being set in Japan (even though everyone is culturally Japanese). However, Konan in Akatsuki has blue/purple/periwinkle hair, and Pein has Orange hair.
Blond hair is quite common in the Naruto universe (Naruto himself, Ino, Temari, Temari's mother and uncle, Tsunade, Deidara, the 4th Hokage), as are gray-haired young people (Kakashi [whose Back Story puts him in his late twenties, Kabuto).
Many other character also have odd hair colors, such as Gaara, Sasori, and Kushina Uzumaki with red, Jiraiya with white (even as a kid), Zetsu and the only-seen-on-a-manga-cover seven tailed-host with green, Kisame Hoshigaki and Konan with dark blue, Suigetsu Hozuki, Sakon and Ukon, Kimimaro Kaguya, Hidan, everyone from the Cloud Village but Yugito (blonde), Karui (red), and the Head Ninja (black), the aforementioned Kakashi Hatake, and Kabuto Yakushi all with silver hair, and Juugo with orange hair. <!— Please, anybody... just provide a group picture. —>
On the cover of Volume 24, Sakon has purplish hair.
Madara mentions that Uzumakis (well, pure blooded ones anyway) all have red hair. Naruto's hair is blond because of his father, and Nagato's changed color due to the effects of the Rinnengan.
Sasuke's hair is black but, at times (especially in Part 1), his hair appears to be blue, probably to fit the rest of his clothes, but later on, his hair is black with blueish tints on it.
Tayuya's hair is red or dark pink depending on who you ask.
Before a certain manga cover was released, everyone assumed Karin's hair was black because of the completely solid black it was shown as in the regular pages, but it showed it was supposed to be bright red. Similarly, True controller of the Six Paths of Pain, Nagato seemed to have possibly black hair in the manga, but when colored, was shown to be blood red/crimson.
Kishimoto has done this, again, with the Mizukage, who looks blond (as in, left uncolored) in the manga but a new cover revealed her to have Chestnut Brownish Red hair.
Then her bodyguards, Ao and Chojuro, who had similarly uncolored hair in regular pages, was shown by a cover to have light blue hair. In fact, Kisame is apparently the same color (though you can't see his hair very often).
Neon Genesis Evangelion has more or less the normal range of hair colors, except for Rei's blue and Kaworu's gray. Then again, neither Rei nor Kaworu are fully human...
It has been suggested by some fans that Rei and Kaworu may, as a result of genetic tampering, have albinism. It's a reasonable assumption (very pale skin, red eyes). Hideaki Anno, however, insists that this was just to make them stand out against the other characters.
Silvana Greone, Shaoli, and Chloe from Noir all have purple hair, albeit in different shades. Silvana's hair is light purple, Shaoli's is dark purple, and Chloe's is in between.
In addition to purple hair, each of these Femme Fatales has a suited alias as well. Silvana's dubbed "The Brutal Princess" or "The Intoccabile", Shaoli's nicknamed "The Cold Blooded Killer", and Chloe is aliased "The True Noir".
In Oku-sama wa Mahou Shoujo, people from Realm have various unrealistic hair colours. The rest of the characters have natural hair colours, though.
In Onegai Twins, this trope is even more jarring than normal - the three lead characters, two of which are siblings, have red, green, and purple hair. This is never mentioned, but their unusual (green) eye colour is several times.
In One Piece, oddly enough, the blue hair of main characters Vivi and Franky is never so much as mentioned, while longer-standing main character Zoro's green hair is ostensibly unusual enough to be cause for mockery. Maybe his detractors just hate him a lot.
Odd hair colours might be considered normal, seeing as there are also a large number of incredibly tall or oddly shaped people like Gecko Moria or Bartholomew Kuma.
There are very few characters with green hairnote Zoro, Keimi, Shojo (of the Saruyama Alliance), Boa Sandersonia, the Baroque Works navigator who took Bon Clay to Little Garden... and some other random character in the background? There're Loads and Loads of Characters. so it might be considered an oddity, whereas blue hair or otherwise is a lot more frequent.
Outlaw Star falls somewhere between Impossible and Plausible hair colors. Most of the characters are white, and any characters of Asian ancestry have black or dark brown hair. On the other hand, we have Harry, who has blue-green hair, and Gene, whose hair is a shade of red that you're very unlikely to find in the real world.
Harry's hair is explainable: he's a bio-android like Melfina, a genetically engineered lifeform created using DNA samples taken from a dead human. And in a setting where that sort of thing is possible, and modifications of all sorts are quite common (so much so that neither Gene nor Jim is surprised when their bounty in the first episode is a cyborg, and Jim has to look up a specific model to figure out his vulnerable spot), if not cheap, then the possibility of DNA tweaking for aesthetic purposes comes up.
Before the Pokémon anime changed to digital animation, James' hair was blue. Now, it's lavender (the dub has made a joke about this). Jessie's hair went from fire engine red to magenta and Tracey's was green even before the switch (just a darker shade, almost black).
Officer Jenny's hair changed from blue to blue-green.
Come on, Nurse Joy's hair is PINK! (All of them.)
Dawn has dark blue hair! That's what the page was named for!
And now we have Cilan, with bright green hair. Then there's his brother, Cress, who plays this trope word for word with blue hair. The third one, Chili, has bright red hair.
Cyrus's hair was blue in the games and the anime; this was lampshaded in the latter.
Crystal from Pokémon Special inverts this trope. She originally had brownhair, but was changed to blue to match her game and anime counterparts. She changed back to brown recently though, which makes people wonder what will happen in the Heartgold/Soulsilver arc..
On the cover of an Emerald volume, her hair was brown, but an image at the end of the saga shows her with dark blue hair. As of HGSS, it stayed dark blue again. But really, either the artist really can't make up his mind or he's trollin' us. Seriously, every time there's a colored shot of her, her hair color changes. Even her first outfit was like this; her jacket would go between white and pink.
In Pretear, secondary characters have brown hair, except for Himeno's step-sisters, who have blueish-green and pink hair. The main cast got hair of different levels of plausibility: brown with some red mixed in (Goh), orange (Hajime), red (Himeno), blond (Shin), golden (Kei, who also has dark skin in the anime), and white (Mannen). Sasame was blond in the manga, but became white-haired in the anime (for a reason, apparently). Hayate's hair went from perfectly normal black in the manga to dark blue in the anime.
Princess Tutu falls somewhere within impossible and implausible. A lot of the characters have odd hair colors (Ahiru's hair is somewhere in between pink and orange, Fakir's is a dark, dark shade of green), but Ahiru could possibly be a stylized redhead and Fakir could have stylized black hair. Mytho's hair is white, but that could be justified, given his magical origins. But then there's Ahiru's friend Pique, who has BRIGHT purple hair — so bright it's hard to think of as stylized black hair — and Autor, whose hair seems to change between shades of blue or purple depending on the scene. And then there's Edel and Uzura's light green hair...but since they're really puppets, that might be justified as well.
Psyren. While in black & white the hair colors seem normal enough, but for the occasional colored section...
Puella Magi Madoka Magica features characters with pink (Madoka), blue (Sayaka), green (Hitomi), bright yellow (Mami), and red (Kyouko) hair, as well as a character with grey hair at a young age (Kyousuke, bonus points for his parents having normal (dark brown) hair). Curtains Matching the Windows is the norm and characters that are magical girls usually have the same color for their outfits (e.g. Sayaka has blue hair, blue eyes, and a blue outfit). The exception of the trope for the most part is Homura who has hair that mostly looks black/anthracite. However it's sometimes depicted as dark purple, which matches her eyes and outfit.
For the most part, RahXephon features almost entirely plausible hair colors. Almost. While Makoto's hair is explained as Albinism, there's still Quon's purple and Ayato's silver/gray hair to get past. Then again, neither of them are exactly human...
In at least the second series of the Ranma ˝ anime, Akane is portrayed with light, rather washed out blue hair. In all other seasons, though, her hair is portrayed as either black or black with navy highlights. Shampoo, on the other hand, is a much better fit for this trope with a long mane of deep blue hair (although in some episodes, mainly the OVAs, her hair is more purple than blue). An anime-only episode reveals that, when she was eighteen, her great-grandmotherCologne had dark blue hair.
Anime Shampoo's exact hair color (blue vs. purple) spurred a vicious debate among fans at one point on message boards.
Ranma-chan's hair is deep, black-highlighted red in the anime, and has been portrayed in almost every color on the manga covers. It's noted in the anime that Kuno can't tell the difference between the red and black hair Ranma has in female and male forms, respectively.
Sieg Hart, Hardner, and (debatably) Belnika are the three blue haired examples of Rave Master. In addition, Haru, Gale Glory, and Let have silver hair. Ex-love interest Reina's hair is green, Nagisa's is pink, and, in the most normal case, Shuda's is cherry red.
The Revolutionary Girl Utena anime has Utena and Mikage (both pink), Anthy (purple), Akio, Mamiya, and Dios (all lilac), Touga (bright red), Saionji (green), Miki, Kozue, and Ruka (all blue), Juri (orange), and Shiori (wine, or perhaps raspberry). Everyone else's hair color is...possible, as most people have brown hair, some have black, and some (notably and implausibly Touga's sister, Nanami) are blonde.
Miki, Kozue, and Ruka all have different shades of blue hair (Ruka himself has two!), with Kanae's mother adding in yet another. Kanae herself, on the other hand, sometimes appears to have very bright green hair. Chigusa and the unnamed main character from the Sega Saturn game have cyan and magenta hair, respectively.
The hair color is so they'll be properly color coordinated.
Rowan/Touma of Ronin Warriors has blue hair, which is unusual since this series tends to avoid giving the main cast odd hair colors. The 4 warlords, however, have brown, white, green, and blue hair.
Rosario + Vampire has Kurumu as a straight example, while Mizore's hair is violet, sometimes close to blue (both of them inherited their hair colors from their mothers), and Moka has both pink and silver hair. Justified, they are not humans and they used to live in the demon world.
Outer Moka and Kokoa's cases are a bit odd. Outer Moka's hair is clearly pink, but it is described as chestnut-brown... And Kokoa's hair is clearly red, but it is described as orange.
Sailor Moon has characters with huge amounts of weird hair colors.
In one of the manga side stories (and the anime special based on it), Chibi-Usa's new classmates actually point out that she has pink hair, which is apparently unusual from the characters' point of view. Makes one wonder if everyone else's hair colors are real, and if so, why nobody finds them odd. Is it only pink that is considered weird?
In the manga, Sailor Jupiter has curly auburn hair. In chapter five, when one of the teachers confronts her about it, she insists that it's natural.
The live-action version made their signature hair part of their costumes, which was the creator's original intention. She had wanted the girls to all have more natural hair and eye colors that would then turn into the fantastical rainbow hairstyles when they transformed. It was supposed to add to the disguise as well as accentuate the magic involved in their transformations.
Zig-zagged with Chibiusa's friend Momoko, who has dark pink hair in the manga, brown hair in the R and S seasons, and deep purple hair in SuperS.
Naoko Takeuchi alternates between using pink or blue hair for Usagi's mother, although one color illustration for the first chapter also depicted her with light brown hair.
Most of the characters in Saijou no Meii have relatively normal hair colours except our Hot-Blooded protagonist Mikoto, who stands out by having purple, spiky unruly hair.
In Saint Beast, several characters have unusual haircolors or two-tone effects. These include scarlet, white, bright purple, dark purple, teal, blue, pink— the entire bubblegum spectrum.
Saint Seiya has a lot of characters with impossible hair colors, most prominently Andromeda Shun, who has green hair. Shun's hair was normal light brown in the manga; it was changed for the animation to make him more noticeable.
In the manga, most of the Gold Saints have blonde hair, and the only exceptions are Dohko, who keeps his auburn hair from the anime, Deathmask, who has silver-grey hair in the manga, Camus, who has red hair, and Shura, who has black hair.
The blondes were eradicated in the anime (with the exception of Shaka) due to too much yellow when combined with the Gold Cloths. But a manga example would be Saga - his hair goes light purple at some points. Also, Shura's a brunette in the manga. As for the anime, a lot of hair get turned blue - Ikki, Deathmask, Aphrodite, Saga, Kanon, and Julian Solo got varying shades, Athena's hair turned lilac, Mu's became pink, Camus and Shura were given green hair, Milo's got turned purple, and Kiki went ginger. Miho got blue hair too. You can tell it's an 8Os anime!
Samurai 7 has (mostly) plausible hair colors: browns and blacks. Then we get to redheaded Heihachi, blond Shichiroji and Kyuuzo, and Ukyo, who actually has blue hair.
And Katsushiro has green hair.
Jun in the original Science Ninja Team Gatchaman had deep green hair that occasionally appeared more black or brownish in early episodes, to the point where fans theorized that her hair was meant to be so black it only SEEMED "green" (or painted that way to save on black ink). The sequel series, all later official artwork, and her cameos in the 2008 Yatterman series threw this into doubt when her hair became a more obvious and brighter shade of green. The '90s OVA mini-series averted this with giving her light brown hair, while the cancelled Imagi film also leaned towards making her brunette.
Mikoto and Nara on School Rumble both have blue hair. Tenma appears to have purple hair.
With the exception of the Locked into Strangeness scientists, all humans in Sekirei have typical Japanese coloring. Most of the titular aliens also have normal colors (brown, blonde) but they're the only ones to have unusual colors such as white, pink, purple, or green. This serves as something of a Hair Color Spoiler, since lilac-haired Miya is revealed to be a Sekirei.
Lampshaded in Seitokai Yakuindomo: in the beach episode, a boy trying to get Suzu's attention explicitly calls her "kinpatsu" (blonde). No one else comments on her hair colour.
Sgt. Frog has Natsumi's pink hair, Momoka's (and her father's) light blue hair, and Saburou's silver hair for the human examples; the humanoid aliens seldom have "normal" hair colours. For the humans, though, this is implied to be the result of dye jobs.
No two Sibyllae in Simoun have exactly the same hair colour (including the two who are sisters). Among them, they've got the whole spectrum covered.
Many characters in Strawberry Panic! have blue hair, as Shizuma complains in this fanvid. Shizuma herself has silver hair; Nagisa's is bright red, Chiyo's is blue-green, Hikari's is very light blonde, and Tsubomi's is pink. In fact, the only major characters with reasonable colours are the raven-haired Yaya and Chikaru.
Haruhi Suzumiya: Most characters hover around the brown-black-auburn spectrum; however, Ryoko, Emiri, Yuki, and Tsuruya have varying colors of green, blue, and grey. Tsuruya's hair colour may just be to throw us off as to her origin, since the other three are discovered to be Human Aliens before we learn Tsuruya's own secret. In the anime and novel color pictures, Yuki's hair is purple. However, nobody appears to find this strange. Could be that others do have strange hair or that their hair is actually just a visual cue for the audience to recognize these characters are not exactly normal. Perhaps, in 'reality', their hair color is something normal?
In Shinryaku! Ika Musume, Nagisa has cobalt blue hair, Chizuru's is more purple, and Takeru's is a dark teal. Ika herself may have hair, matching her blue tentacles, depending on whether or not that stuff over her apparent eyebrows is hair.
While the series does use regular colours in many cases, there are several characters in Soul Eater with unusual hair colors, like Chrona and Kim (pink) and Black☆Star (blue). And the titular character, Soul, has white hair. The worst example would be Kid's black-and-white striped hair, though this is justified as the stripes indicate his true nature. Presumably were he actually human, his hair would just be a reasonable plain black.
In Sukisho, there's a pretty even mix between cast members with normal hair and those with weird colors. The series main characters, Sora and Nao, have blue and pink hair respectively. And then there's the little kids, two of whom also sport cotton candy colors.
The girls in the Tenchi Muyo! series all have odd hair colors except for Mihoshi, who is blonde. Ryoko has what appears to be a very light shade of teal hair, Washū has pink hair, Ayeka has dark purple hair, Sasami has a teal-blue shade of hair with it's brightness depending on the series (sometimes it looks like light blue-green and sometimes it looks a bit sky blue), and Kiyone has dark green hair, though it can look black at times.
They're all aliens anyway, though.
Washū also has red hair, not pink, so she goes under barely normal in that area. Mihoshi is a brown-skinned blonde, and Washū is an age-bender...
Subversion of the escape clause: Aeka's purple hair is revealed in the manga to be dyed... it's actually the same light blue as her sister and mother.
Why is an alien bluenette dying her hair purple, you ask? To match her second mother's (Jurai royals practice polygamy) naturally purple hair! Said second mother is a full-blooded human from 13th century Japan, a fact which takes the escape clause, rips it into small bits, incinerates the bits with a flamethrower, and then urinates on the ashes.
Allegedly, it was about tweaking her available genetics to resemble her second mother, Funaho (who has black hair), as much as possible, hence her father's purple-hair DNA traits were turned more dominant.
Tengen Toppa Gurren Lagann is rife with examples of Anime Hair, since it's an over-the-top, hot-blooded middle finger to science. Heroes Simon and Kamina both have blue hair (though Simon's looks kinda black), Yoko has brick red hair (as does Gimmy), Leeron's is aqua, Darry's is cotton-candy pink, Kittan's is blond and black.
Interestingly, in the manga, Zakuro is said to have black hair at one point, suggesting purple is, indeed, here just for convenience. Ryou Shirogane, on the other hand, is confirmed to have golden hair and blue eyes via the scene where Ichigo thinks he is the Blue Knight, citing said features as a similarity. Slightly odd, since this is the typical appearance of a "gaijin", which Ryou doesn't seem to be (he did live in America, but it is implied that his parents were Japanese).
Toradora! has a character who normally has green hair rebel by dying his hair blonde, and everyone is shocked by this. He eventually changes it back, though In-Universe it's actually black hair.
The main character of Toriko has light blue hair, but special mention has to be given to Sunny's white hair with pink, blue and green stripes.
Most of the Trigun characters have realistic hair colours, but Legato has blue hair and yellow eyes to underline his weirdness, and some of the "mutant" characters have green hair, among others.
The heroines of Studio Pierrot's Magical Girl series have these:
Yuu from Creamy Mami is a weird case. When transforming into her Magic Idol Singer form, she gains curly lavender hair, but in her everyday form as a normal girl, she already has teal hair.
While most of the characters of Future GPX Cyber Formula have natural hair colors, Bleed Kaga has green hair with orange streaks and a black braid tail for most of the series and Henri has silver hair with a red steak on a strand of his bangs.
In Umi Monogatari, Kanon's hair is a dark blue color, but becomes a lighter tone when she transforms. Played straight with Warin.
Urusei Yatsura has green-haired characters, though this is justified because they're aliens. The humans all seem to have natural hair colors.
Hair colors in Weiß Kreuz are mostly just implausible — Aya, Manx, and Schuldig (justifiable as he is meant to be a white westerner) all have bright red hair, and Yoji and Omi are blond — but some members of the supporting cast have outright impossible hair colors, such as Ouka's blue hair and, from the Oddly Named Sequel series Weiß Kreuz: Glühen, Tsuji's green hair.
The hair may be why strangers assume she's a foreigner.
Well, her adopted father did say he picked up overseas...
The eponymous character of Yu-Gi-Oh! has three-colored hair — black, gold, and pink. Aside from that, the show tends more toward weird hair styles then weird hair colors — indeed, some of the odder hair colours from Season 0 (such as Kaiba's bright radium-green hair) were recoloured to something more probable for the better known later seasons.
Though Kaiba's green hair is an Adaptation Dye-Job. Whenever he shows up somewhere on the cover of the first 7 manga season 0 was loosely based on, he clearly has brown hair.
Sho/Syrus and his older brother Ryo/Zane from Yu-Gi-Oh! GX, as well as Blair/Rei all have blue hair, but like the previous series mostly relies on reasonable hair colours, and the haircuts are toned down in comparison. In Yu-Gi-Oh! 5Ds, Luca/Luna and Lua/Leo both have green hair (which, considering their wealthy parents, could be dyed), and Bruno has blue... these being extremely light cases considering villains Aporia and Paradox, who both have utterly impossible hair which is silver-red and yellow-purple respectively.
In Yu-Gi-Oh! ZEXAL, blue hair apparently runs in Shark's family; both he and his sister have it.
YuYu Hakusho's human characters have every possible natural hair color (except Genkai, who's graying now but originally had pink hair), while the more fantastic characters usually have more fantastic hair colors. Both Kurama and Kuwabara have red hair, for example, but they're very different shades. To be fair, however, Genkai originally was strawberry-blonde.
Botan's is even lampshaded.
Koto: Why not focus on something you're good at, Honey? Like dying your hair unnatural colors?
She still insists it's natural.
Kurama's hair is black (or dark blue) in the manga.
Yamada-kun and the Seven Witches is a major offender. The only one in the main cast who has a plausible hair color is Shiraishi, and even she is a bit abnormal as she is a Japanese girl with blonde hair.