Single photon detection requires fully adapted night vision, and that implies rod cells only detection, and rods are black and white detectors. The cone cells do the color detection, and they only work well in daylight. That's why we see in black and white only in dim light.

Interesting that the eye contains a photon detection system and a photon wavelength detection system. You could get a lot of information out of that, enough to avoid getting eaten by unfriendly critters both day and night.