Research conducted in recent years has documented the widespread presence of various forms of color vision in species across the animal kingdom. These studies advanced our understanding of the basic biological mechanisms underlying this sensory capacity and have provided some insights into utility of color vision in the natural world. This chapter draws information from all these various sources to reveal what has been learned about the evolution of color vision. In doing so, we examine the extent and nature of animal color vision, describe various structural features of eyes and photoreceptors that condition color vision, look at photopigment opsin genes and their color vision concomitants, and comment on specific cases where progress has been made toward understanding the functional utility of color vision. Although results from a wide range of different species are considered, we focus particular attention on issues relevant to the evolution of vertebrate color vision.