Not only are they masters of disguise, they have eyes which turn independently of each other so that it is capable of looking forward and behind at the same time.
Then way they change colour automatically with no effort on their behalf is amazing.
This is the Common Flap-necked chameleon, the largest of our species and these are some of the changes in colour I have been able to take photographs of. The first one is how they normally look.
For more information on them, please go to: http://saphotographs.blogspot.com/2009/03/flap-necked-chameleon_10.html