Their skin cells contain dark pigments that expand in bright light and contract as light dims. As a result, largemouths in direct sunlight usually have dark and distinctly patterned backs with prominent lateral-line stripes. Bass fully shaded from light tend to be silvery with indistinct markings. The amount of light that hits ta fish's eyes and the direction it comes from modifies pigmentation. If light bounces from the bottom, pigment cells on a fish's back expand less.
Blind bass show extreme changes in coloration because the pigments only react to direct light.
Normally sighted bass modify their pigmentation to reduce contrast with background light. Bass over dark bottoms retain the dark pigments created by direct sunlight. Their backs lighten if these fish move over bright, sandy bottoms. Such changes keep them camouflaged by reducing contrast wherever they go. Those in brown-stained waters take a brown hue, while those over black rock darken.