When does a chameleon change colour?

Chameleon - will change colour when it senses danger. This remarkable member of the lizard family can change colour to match its background or at least to become almost unrecognizable. The ranges of colours and patterns of the various species differ widely but most chameleons can become yellow or cream green or dark brown. They can also adapt spots either dark or light depending on the colour of the ground. Apart from its response to danger the chameleon will change colour according to the light and temperature. This mechanism is controlled from the nervous system and involves the dispersion or concentration of colour pigments in the creature's skin.