Do trout see blue, green and yellow? How is their colour vision different from a bass's?

Trout have the best-documented — and probably the richest — colour vision of the fish on this site. An adult rainbow carries three working cone types — blue, green and red — where bass and walleye make do with two and read blue as dark; juveniles add an ultraviolet cone that mostly disappears with age. So a trout genuinely sees blue. That matters in big, clear lakes, where blue and green light penetrate deepest: blue-and-silver and green-and-silver spoons are trolling staples for lake trout and lake-run rainbows. In streams, green means olive — the colour of most nymphs, sculpins and the flies that imitate them. Yellow and gold are visibility colours: a gold blade or yellow-bodied spinner in stained or low-light water. Still, size, silhouette and drift come first; colour is the third thing a trout judges.

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