Necessary in almost all organisms, such as certain types of animals change color to camouflage themselves against environmental or animal of some kind using skin color to communicate, including reproductive control heat.
Essential to life virtually all types of animals change color. To disguise themselves with something like that environment. Or some animals use to communicate color reproduction to control the heat.
Almost all necessary for organisms such as some animals change color. To camouflage themselves with the environment. Or some kind of animal skin use to communicate, reproduction, including heat control.