How do chameleons change color?

Sarah,

In answer to question 2 first, yes, many other animals change colour, some in very short periods of time (cuttlefish, squid etc. are brilliant at changing colours in rapid succession) and some that take a bit longer (plaice, flounders and other bottom dwelling flatfish often match their surroundings very accurately after a couple of minutes or so).

The pigment and light reflecting cells in animals (mainly cephalopods like the squid, fish, reptiles like the chameleon and amphibians) are called chromatophores. For animals like cuttlefish and squid that change colour rapidly, either to hide / sneak up on prey (known as cryptic (this simply means ‘hidden’) camouflage) or to signal to a mate / rival etc, this is known as physiological colour change and is controlled by muscles around each chromatophore squeezing and distorting the shape of the chromatophore (a bit like the muscles around the eye squeeze the lens to enable us to focus).

Chameleons change colour through a rather different mechanism, which has far more to do with cell signalling (this is part of a complex system of communication that governs basic cellular activities and coordinates cell actions), so chameleons change colour as a result of mood (anger, mate attraction etc.), rather than to blend into their background.

The way in which chromatophores are pigmented and control this is rather complex. A quick scan of  this article http://en.wikipedia.org/wiki/Chromatophore seems to be fairly accurate but it may be a little complex for you. Have a look anyway.

Best wishes,

Dave.