Gaze at the vivid yellows, blues, and psychedelic swirls of a single emperor angelfish and you'll sense the whimsy of evolution. Go on to explore its home in lush coral reefs and you'll soon hit sensory overload, assaulted by colors and patterns that range from sublime to garish. Coral reefs are unquestionably the world's most colorful places. But why?
Scientists have long known that color plays a role in sexual selection and warning of danger. But only in the past decade or so have we begun to understand how wavelengths of light (and therefore color) appear at different depths and how various marine creatures' eyes perceive this light and see each other—far differently than humans see them.
To document how reef animals use color, I joined photographer Tim Laman for a total-immersion course off Fiji and Indonesia. It was an eye-opener, with virtuoso dis-plays of color at every turn. Beyond the world's reefs, where waters are turbid or murky, most creatures use nonvisual means of communication such as smell, taste, touch, and sound. But in the clear, sunlit waters of coral reefs, light abounds, vision predominates, and animals—both sighted and blind—drape themselves in blazing color not only to entice mates or threaten foes but also to advertise their services, evade predators, catch prey, even hide in plain sight.