I saw a real cool video of a chameleon who changes colors every time it touches a different colored pair of glasses. How do you suppose they do that?

http://www.youtube.com/watch?v=KMT1FLzEn9I

Some (but not all) chameleon species are able to change their skin colors. Different chameleon species are able to change different colors which can include pink, blue, red, orange, green, black, brown, yellow and turquoise.[6][7]

Some varieties of chameleon - such as the Smith's dwarf chameleon - use their color-changing ability to blend in with their surroundings, as an effective form of camouflage.[8]

Color change is also used as an expression of the physiological condition of the lizard, and as a social indicator to other chameleons. Some research suggests that social signaling was the primary driving force behind the evolution of color change, and that camouflage evolved as a secondary concern.[9][10]

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 colorless 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 contained in melanophores is situated even deeper under the reflective iridophores. The melanophores influence the 'lightness' of the reflected light. These specialized cells are full of pigment granules, which are located in their cytoplasm. Dispersion of the pigment granules in the cell grants the intensity of appropriate color. If the pigment is equally distributed in the cell, whole cell has the intensive color, which depends on the type of chromatophore cell. If the pigment is located only in the center of the cell, cell appears to be transparent. All these pigment cells can rapidly relocate their pigments, thereby influencing the color of the chameleon.