I've read that chameleons actually use colors to communicate with one another. They can't communicate like us obviously and they don't even have ears. But they can create vibrations and they can change their colors to give messages to those in their surroundings.
For example, it's not a good idea to get close to a yellow chameleon because it means that he is not very happy at the moment. Black is even worse and indicates aggression, the chameleon is feeling threatened. Green means that the chameleon is relaxed and happy.