As chameleons are able to change the color?
The colors associated with the special skin cells.
Upstairs
Inside these cells there are nanocrystals. They are like little reflectors come in different shapes and sizes. Chameleons are able to change the position of these crystals and reflect light of different wavelengths.
And need is a chameleon not only for masking. The chameleon changes color to communicate with other chameleons.
See also:
The most cunning hunters: what happens to the victim in the embrace of a boa constrictor
Fish-invisible can “disappear” for 2 seconds