Mammals are really unlucky when it comes to easily accessible pigments. There are no simple gene switches that would give mammals fun anime colors, so brown, white, and black are all we get. :rage-cry:
Red eyes are due to a lack of melanin allowing you to see the redness of blood vessels. Likewise, a lot of animals that are blue or green don't actually have that pigment but reflect light a certain way.
Mammals are really unlucky when it comes to easily accessible pigments. There are no simple gene switches that would give mammals fun anime colors, so brown, white, and black are all we get. :rage-cry:
There's also yellow, reddish (in albinos), blue, green, gold, and others I'm sure.
Red eyes are due to a lack of melanin allowing you to see the redness of blood vessels. Likewise, a lot of animals that are blue or green don't actually have that pigment but reflect light a certain way.