The background color covers the back, sides and fins and serves to highlight the lighter gray spots. Trout in large lakes are sometimes so silvery that the spots are difficult to see. Spotting is usually more intense on small fish. The caudal fin is deeply forked. The mouth is large and terminal with strong teeth on both jaws.
Colors vary greatly, with patterns depending on habitat, size and maturity.
Stream residents and migrant spawners are darker and have more intense colors than lake residents or nonspawners. Lake residents tend to be silvery. A mature rainbow is dark green to bluish on the back with silvery sides. The reddish horizontal band typifies the species. The belly may be white to silvery.