The functional impacts and genetic bases of the human photopigment polymorphisms have been intensively studied and debated. Even though they attract much attention, photopigment polymorphisms that cause significant changes in color vision are relatively infrequent in humans and effectively absent in other catarrhine primates. By contrast, photopigment polymorphisms are near universal in New World (platyrrhine) monkeys and they also appear sporadically among the more primitive strepsirrhine primates. Recent studies of these pigment polymorphisms, particular those of the platyrrhines, have significantly enhanced our understanding of a number of fundamental aspects of color vision. Among other things, these polymorphisms have (a) been exploited to detail the relationships between opsin gene structures and pigment spectral tuning, (b) been used to illustrate how X-chromosome inactivation can serve as a tool for adding perceptual capacity, and (c) provided real insights into the evolution of primate trichromacy. As well, these photopigment polymorphisms now provide an attractive resource for studying the ecology of primate color vision and a framework for testing hypotheses about the organization of primate visual systems.