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There are a lot of Japanese shows and games where people have many different hair colors and eye colors. There are even cartoons and games where people come in every skin color in the rainbow and beyond.

For my story, I'm writing about a transplanted human population that started all of their civilizations on another planet. I was wondering would it make biological sense for humans or near-humans or even primates in general to possibly mutate and have their hair, skin, and eyes come in every single color imaginable? Or are human skin tones and hair colors limited for a specific reason. Why is a person with natural blue eyes and yellow hair possible, but a person with natural yellow eyes and blue hair not possible?

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  • $\begingroup$ possible duplicate worldbuilding.stackexchange.com/q/44371/30492 $\endgroup$
    – L.Dutch
    Nov 24 at 20:11
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    $\begingroup$ We've hosted many Qs about hair color and skin color. The simple answer to your Q is "no" and many of the previous Qs have the hard-science to prove it. So I need to VTC, because the research is already there (and trivial to find) and this is a duplicate of multiple Qs. $\endgroup$
    – JBH
    Nov 24 at 20:23
  • $\begingroup$ Note, however, that you're asking if it's reasonable to transpose Earth biology onto an alien biology. (a) We one data point to work with, Earth, so the only official answer is "we don't know." (b) The help center states that we're here to help you build imaginary worlds. Trivially, on your world you can have any color hair and skin you want and there's nobody on Earth who can say you're wrong. Only that here on Earth, it isn't possible. (c) As for mutate? Well - parrots have lots of colors, who's to say? But we're talking about evolution, not mutation per se. So, rule of your world. $\endgroup$
    – JBH
    Nov 24 at 20:27
  • $\begingroup$ @L.Dutch, that question is about a person having multiple different tones and colors in their hair or skin (essentially striped like a zebra). I'm asking for only one hair color or skin color but the color is one humans don't naturally have. $\endgroup$
    – Rhymehouse
    Nov 24 at 20:35

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You want all kinds of random skin, eyes and hair. Patchy. Not pretty except by accident or effort. Here you go:

Recycling this fine answer.

The skin color is an unintended byproduct.

Practical reason for genetically engineering exotic skin colors in humans?

Your humans have been genetically engineered for disease resistance, self-synthesis of certain vitamins and amino acids, slightly different neural synapses that benefit from ambient low levels of nitric oxide, and other things. Genetic engineering is usually done at the early zygote stage by extracting one or more cells, engineering them and then adding them back to the zygote, so the descendants of that engineered cell spread around and give rise to engineered populations "homogenously" within the organism.

It is not really clear which of the engineered cell populations interact but a result is unpredictable skin and hair coloration, which occurs semirandomly. Sometimes it is all one color. Some people are several colors or have harlequin like patches, apparently according to the establishment of engineered populations of cells. It is not uncommon for the coloration to drift and change with the years. More rapid and dramatic changes can occur when people use "aftermarket" GMO; infusions of engineered stem cells which are intended to spread thru the organism and engraft, conferring new properties. The aftermarket GMO cells are sort of like apps - they are made by a variety of proprietors and vary greatly in quality, efficacy, side effect profile, and cost.

The genetic engineers overseeing GMO projects view this skin color issue as harmless and irrelevant; certainly more harmless than other side effects of the engineering endeavor which occupy most of their remedial efforts.

That stuff all went down on the prior planets. Some of these planets had better genesmiths than others. Some aftermarket mods done on a whim, or out of necessity have integrated into the genomes of the bearers, and their descendants. The original rationale for the gene edits and additions have often been forgotten with time. Or mixed up with successive generations of interbreeding individuals.

Your people live with the unplanned legacies of their ancestors.

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Human Pigments

Links to wiki for reading: Human eye color Human hair color Human skin color

Humans have a range of eye colors, but only one pigment, melanin, is present. A higher concentration causes a darker color. The remaining color variation comes from Rayleigh scattering. To get yellow eyes, you might need other pigments, that are not normally produced by humans. Similarly, human hair color has only a few pigments, all melanins. There is some variation in the melanins, so we can get dark hair, blond hair, or reddish hair, but that is about it. Melanin can't make green hair to my knowledge. You might need other pigments to do that, which are not normally produced by humans. Finally skin tones are mostly influenced by melanin (darker to lighter skin) as well, and also are affected by the color of the tissue beneath (the dermis, veins and arterioles, etc. will affect blueish and reddish tone)

So: Human coloration is limited for a specific reason: because we only produce certain pigments. If we take a look at birds for example, they produce other pigments we don't have to get striking colors:

So the question remains about how to obtain these pigments. You imagined mutations that produced other colors, but we have to consider what it mutation would produce such a color change, and why it would become distributed over the population. Additionally, different pigment families can produce different colors, so you will have to think about how this could have happened. If we stick with melanin your color range will be limited to brownish / yellowish / reddish colors for example. I have a feeling its not very likely for us to spontaneously gain the ability to synthesize carotenoids, for example, which color leaves, carrots, and salmon orange.

Thus mutation seems unlikely to give outlandish colors, if we are starting with modern human stock. Maybe a better solution is some sort of handwaving or genetic editing. Of course the question there is "what is considered natural".

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  • $\begingroup$ Somewhere on this stack there is a question about why birds can have green feathers, but green fur seems to be difficult. Other than, IIRC, a critter with green mold that makes its fur look green. Something about the size of hair strands and refraction, but I don't recall exactly. Green fur would seem an obvious camo advantage. $\endgroup$
    – Boba Fit
    Nov 24 at 20:51
  • $\begingroup$ Yeah, I wasn't considering other methods to get things like green fur in this answer. Of course, if you can grow mold on your head, you can dye it as well ;) But is that "natural"? $\endgroup$ Nov 24 at 21:21
  • $\begingroup$ Humans produce two kinds of pigments, the brown or black eumelanin and the reddish phaeomelanin (which gives the color of lips, areolas and other hidden bits). $\endgroup$
    – AlexP
    Nov 24 at 22:42
  • $\begingroup$ Believe it or not, yellow eyes are possible, just rare. We usually call them "amber" or "gold", much like yellow hair is "blond" $\endgroup$
    – No Name
    Nov 25 at 5:45

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