It only takes differences in three amino acids to tune cones in the retina to be sensitive to red or green light, the team found. "In the long term, this knowledge may help researchers understand how genetic variations alter color perception and contribute to color vision deficiencies and other visual disorders." The red and green cone pigments are very similar molecules. They took cryo-electron microscope images of the red and green cone pigments in the macaques, then created digital models of them. This close examination also revealed a new structure that may explain why your color vision doesn't 'wear out' after a while in a bright room.