Pigments are what dictate the coloration of an organism. The chief pigments found in animals include guanine, which is expressed as the color white or as an iridescent hue, the carotenes, which range from yellow to red, the melanins, which are perceived as brown or black, and the hemes, which are responsible for the reddish hue of blood hemoglobin. Some of these pigments function in various physiological activities as well as providing color. Most notable in this regard are the carotenes, which are important in the vitamin synthesis of animals, as well as chlorophyll synthesis in plants.