Book excerpt: A chameleon’s skin has two layers. The top layer contains pigments (pink, blue, red, orange, green, black, brown, light blue, yellow, turquoise, purple), and the bottom layer contains guanine crystals. They are able to change colors by changing the space between these layers, which changes the wavelength of light reflected off the crystals and the color of the skin (kind of like a rainbow). Color change functions as camouflage to protect chameleons from predators such as birds or snakes. They change their color to blend in to avoid observation. They can change both their color and their patterns to resemble their surroundings or disrupt the outline of their bodies and remain hidden from sight. If detected, chameleons actively defend themselves. They adopt defensive body posture, try to appear larger, and warn with an open mouth. They will kick and bite and sometimes vocalize during their threat displays. Their color changes are also used in social signaling. These color changes signal their intentions to other chameleons. They show brighter colors when displaying aggression and darker colors when they give up. It is how they communicate.