Alan: That poses an interesting problem. What kind of pigments would a non-human use? I'm think something in UV range made from fluorescing minerals or something like that. There are some artist pigments that change colors depending on angle of light. Looks way-cool in gallery. Move your head a bit and what was one color changes to another. I'll see if I can find example from a gallery show we had last spring. here's a car I photographed painted in one such style of paint http://members.iinet.net.au/~shahjen/images/small.jpg
