How squid choose and hold particular skin colors to help camouflage themselves remains unknown and is particularly interesting because the animals are completely colorblind.

When I was young, Jupiter had exactly 12 moons. Just not finding an obvious mechanism for color vision in the squid, doesn't prove they are unable to sense color.

I expect such a mechanism to be discovered, because the idea of a color changing and camouflaging animal that is color blind, is preposterous.