Any of a class of yellow, orange, red, and purple pigments that are widely distributed in nature, including vegetables, fruits, insects, fishes, and birds. Most of these pigments are carotenoids, which are generally fat-soluble unless they are complexed with proteins. In plants, carotenoids are usually located in quantity in the grana of chloroplasts in the form of carotenoprotein complexes. Carotenoprotein complexes give blue, green, purple, red, or other colours to the outer surfaces or eggs of crustaceans, such as the lobster and crab. Echinoderms, nudibranch mollusks, and other invertebrate animals also contain carotenoproteins. Some coral coelenterates exhibit purple, pink, orange, or other colours due to carotenoids in the calcareous skeletal material. Cooked or denatured lobster, crab, and shrimp show the modified colours of their carotenoproteins.