How Do Blind Worms See the Color Blue? Eyeless roundworms may have hacked other cellular warning systems to give themselves a form of color vision. In an experiment, the blind roundworm C. elegans did not try to wriggle away from a beige version of the P. aeruginosa bacterium, which can kill it and is usually colored bright blue.Credit...Eugene L. Q. Lee March 4, 2021 In the warm, fetid environs of a compost heap, tiny roundworms feast on bacteria. But some of these microbes produce toxins, and the worms avoid them. In the lab, scientists curious about how the roundworms can tell what’s dinner and what’s dangerous often put them on top of mats of various bacteria to see if they wriggle away. One microbe species, Pseudomonas aeruginosa,