User blog comment:Adsper/All Possible Mobs/@comment-2605:A000:A487:4C00:658F:5304:B04A:6318-20171228172251/@comment-2605:A000:A487:4C00:38A9:8CE1:A3CA:74FB-20171228223646

There is actually evidence in the form of pigments. Fossilized remains of the skin show pigment levels in it (showing what color they are), and thee color can be visible in the fossils.