Why does a chameleon change color?

The chameleon is a type of lizard whose color rangers from green to cream to dark brown. It often has patches of light color on a darker background. The color of the chameleon's skin changes to blend in with its surroundings, and so helps to hide it from its enemies. Some other types of lizards also change color.
The skin of the chameleon contains small cells closely packed together, which are filed with small granules of pigment(coloring matter). The pigment seems to react to changes in the environment, such as heat and light, and to changes in the animal's mood, such as anger or fear. In hot sunlight the skin will turn dark. If the animal is excited, Its skin will change to dark and light patches.