Birds, fish, reptiles, amphibians, insects? Sure. But no mammals.
So I had to google it. Apparently, there is a sloth that moves around so slowly moss grows all over it and it doesn’t care. So it may appear green, but only in the sense that it wears it.
Good article here https://nature-notes.riverlegacy.org/how-come-there-are-no-blue-or-green-mammals
So I skimmed that and it seems the tldr is mammals have melanin (and I’m guessing the other animals don’t)
Great read! That explains a lot.
I’ve been deep diving a bit myself and found this article that explains another thing that’s puzzled me over the years. Some birds have crazy vibrant coloration that almost glistens, like peacock feathers. Outside of the zoo, I’ve noticed it a bit in common grackles. They look black on first glance, but when you study them closely, they have this kind of purple sheen around their heads. Apparently, it’s still melanin at work here, but it’s structured in a very special way.