Growing to around the length of a butter knife, peacock mantis shrimp have rainbow shells—usually blue, green, and yellow—and red legs. Their purple eyes sit on top of stalks above their head ...

Human eyes rely on three types of photoreceptors to detect color: red, green and blue. Mantis shrimp, on the other hand, have between 12 and 16 types of photoreceptors. This allows them to see a ...