Well in humans, skin gets its colour from a pigment called melanin which is made from special cells in the skin. And in animals, I believe they can actually manipulate it?
This is an extended thinking portion in my textbook, and I would really like to know why this is. I'm not too sure what the answer to this is, and unfortunately, there is no answer to extended thinking in my textbook. I've been trying to figure this out for some time now and I'm completely stumped.