Wikipedia: [All chameleon species are able to change their skin color. Changing color is an expression of the physical and psychological condition of the lizard, not, as is commonly believed, to match their surroundings.[5] Thus, the old joke about a chameleon suffering a fatal injury upon setting foot on a plaid is based on a false premise. The colour also plays a part in communication.
Chameleons change their colour in response to light exposure and ambient temperature, as well as to express their mood. Emotions and attraction of a mate can induce the colour change.[6]
Different chameleon species are able to change different colours which can include pink, blue, red, orange, green, black, brown and yellow. [7][6] Chameleons are naturally coloured for their surroundings as a camouflage. However, recent research has indicated that Chameleons may use colour changes as a method of communication, including to make themselves more attractive to potential mates.[8]
Chameleons have specialized cells, collectively called chromatophores, that lie in layers under their transparent outer skin. The cells in the upper layer, called xanthophores and erythrophores, contain yellow and red pigments respectively. Below these is another layer of cells called iridophores or guanophores, and they contain the colourless crystalline substance guanine. These reflect, among others, the blue part of incident light. If the upper layer of chromatophores appears mainly yellow, the reflected light becomes green (blue plus yellow). A layer of dark melanin containing melanophores is situated even deeper under the reflective iridophores. The melanophores influence the 'lightness' of the reflected light. All these pigment cells can rapidly relocate their pigments, thereby influencing the colour of the chameleon.
