A mantis shrimp has twelve kinds of colour receptor in its eyes, and we have three, so for years people assumed it lived in a world of colours we can’t imagine. Then, in 2014, a team in Australia trained some mantis shrimp to pick out one colour of light from another for a food reward, and they turned out to be worse at it than we are. Not slightly worse: colours that a person tells apart easily, the shrimp couldn’t. The best guess is that it doesn’t compare its channels against each other the way our brains do. It just notices which receptor fired and takes that as the answer, quickly and cheaply, like reading a label instead of mixing paint. All that equipment, and what it buys is not a finer eye but a faster one, built for an animal that needs to know “that’s the red one” before it strikes, and never needs to know how red.