Another common use of color in chameleons is to signal receptivity (or lack thereof) to mating.
Among panther chameleons (the star of this post), the female is typically more drably colored than the male. However, when she is ready to be bred, her color changes to a uniform salmon pink:
The calyptratus, or veiled, chameleon is even more accommodating with its color changes. There, the female takes on a bright coloration (typically turquoise and yellow-green against charcoal) to indicate she's ready to be bred -- and then, after mating successfully, dims to a 50-shades-of-grey theme to prevent subsequent attempts.
In the wild, chameleons are typically solitary, highly territorial creatures. Given the risks involved in crossing from one's own tree to that of a prospective mate, it's not a journey to be taken lightly -- hence the advantage in knowing in advance whether the trip is going to be worth it.
A quick Google search of chameleon images reveals the wide range of [non-towel-related] coloration among
panther and
calyptratus chameleons.
