Human color perception is widely understood to be based on a neural coding system involving signals from three distinct classes of retinal photoreceptors. This retina processing model has long served as the mainstream scientific template for human color vision research and has also proven to be useful for the practical design of display technologies, user interfaces, and medical diagnosis tools that enlist human color perception behaviors. Recent findings in the area of retinal photopigment gene sequencing have provided important updates to our understanding of the molecular basis and genetic inheritance of individual variations of human color vision. This Element focuses on new knowledge about the linkages between color vision genetics and color perception variation and the color perception consequences of inheriting alternative, nonnormative, forms of genetic sequence variation. ‘… the book is a comprehensive account of research and current thinking regarding the possibility of human tetrachromacy. By bringing together the literature in this way, the authors make a compelling case for a change in thinking and push the field to expand on the standard trichromatic model of human colour perception.’ Stacey Aston, Elements in Perception This Element focuses on new knowledge about the linkages between color vision genetics and color perception variation.