By filming color changes and examining the chameleons' skin using transmission electron microscopy, the scientists were able to see two layers of skin with iridophores. It turns out that tiny guanine nanocrystals boast very specific spacing between each crystal that in turn reflects different layers of light-shorter spacing reflects blue light, longer spacing red. By interacting with yellow pigment cells (xanthophores) in the skin, greens and oranges emerge. What's more, some less-organized crystal spacing may even reflect near-infrared light, helping to cool the chameleons. "We need to continue investigating the chameleons," Milinkovitch adds, "because part of the answers are there and nowhere else."
Source: Newser