He who understands baboon would do more for metaphysics than Locke.
(Charles Darwin (Barrett 1974:281))
'Colour' in the first and foremost sense means red, green, yellow, blue, black, and white, and to study colour in this sense visual scientists must rely on the reports of human subjects. Therefore, the assumption that human colour vision provides the reference point for understanding colour, both in philosophy and in visual science, is justified. Care must be taken in applying the assumption, however, because certain distinctive features of colour (for example, hue opponency) appear to be traceable to our psychophysical and biological makeup, and from the psychobiological perspective many of the discriminative behaviours and physiological structures involved in human colour vision are not unique. Moreover, from the perspective of evolutionary biology, human colour vision-indeed primate colour vision in general-is not the norm. These psychobiological and evolutionary dimensions indicate that, although it may be impossible not to take colours as we see them as the standard, a fuller understanding of colour can be had only by situating human colour vision within a wider comparative context.
Questions immediately arise, however, when the attempt is made to enlarge our perspective to a comparative one. We