Atma

“blue whale, the ocean is not blue. Cone cells are unique to vertebrates, but other animals have wavelength-specific photoreceptors that play a similar role. Surprisingly, the cephalopods—octopuses, squid, and cuttlefish—have just one class of these, which means they are also monochromats.[*2] They can rapidly change the colors of their skin yet are unable to see their own shifting hues.”
― Ed Yong, An Immense World: How Animal Senses Reveal the Hidden Realms Around Us