Rough epidermis (outer skin) of a chameleon contains cells known as chromatophores that have pigments in them. They can take on yellow, red, blue and brown hues. Some of these pigments are concentrated in small clusters under various parts of the skin, whereas some are spread evenly beneath the skin in the form of minute particles. The color assumed by the chameleon depends upon the pigments of which colors have been spread and which have been pulled back. For example, if red pigment is spread beneath the entire skin and the rest are held back the chameleon appears red.
A question would naturally arise: What causes the spreading of a particular pigmentation while holding back other pigments? The hormones produced by the pituitary gland of the chameleon are found to be responsible for this phenomenon. However, the scientists have no answer to the question how the chameleon’s hormones spread pigments of some color while holding back those of the other colors. They know that about 100 species of chameleon can change color but not at their will. Nature has not delegated to chameleon the capability to change color at will – but has reserved this power in its own hands.