Color pervades our visual sensory world, yet our understanding of the neural basis of color perception, starting with the retina and on through the multiple cortical areas that subserve vision, is still incomplete. The L, M, and S cone photoreceptors, being the cellular entry point for trichromatic vision in humans and other primates, have been studied in a variety of ways to reveal their relative numbers, their spatial arrangement, and their anatomical connectivity. We review work in these species that has linked mapped cone mosaics directly to functional properties such as single neuron responses in the retina and color percepts arising from cone-targeted microstimulation. We also highlight important technical issues that constrain access to single cone photoreceptors for functional studies.