Although it is commonly believed that chameleons change color to blend with their background, there is a breed of chameleon that change color according to their mood. The male Yemenese chameleon, normally yellow, green or orange will turn lighter when they are comfortable and in the company of a compatible female. And when they are feeling amorous, they turn brighter shades to make themselves appear larger and garner more attention.
If they are cold, exposed and anxious, they will turn darker, as will their moods. Interestingly, the brown-black pigment that darkens their skin is called melanin, the very same pigment that causes a human suntan.
Although humans are not thought of as particularly colorful, we obviously come in a limited assortment of shades, but we do have the propensity to change those shades depending on our health, physical and mental, as well as our emotions.
For example, we turn yellow with jaundice, red or purple with rage, orange when we eat an overabundance of carrots, greenish when we are nauseous, blue when we are oxygen-deprived or excessively cold, and the most telling of all, a blushing pink when embarrassed or otherwise aroused.