Scientists have long believed tarantulas can’t see colors. But the idea puzzled Saoirse Foley, a biologist at Carnegie Mellon University in Pennsylvania. That’s because these spiders come in a variety of different shades. “I wondered why tarantulas have such wonderful colors if they can’t see them,” says Foley.

Foley looked at how green and blue coloring had evolved, or developed over time, in tarantulas. The green hue seemed to act as camouflage, helping tree-dwelling tarantulas blend in with their surroundings. The blue color possibly served to attract mates. Foley was also surprised to discover that the spiders’ eyes contain light-sensitive molecules called opsins, which are important for color vision. These findings seem to hint that tarantulas may not be colorblind after all.