<P> Nothing categorically distinguishes the visible spectrum of electromagnetic radiation from invisible portions of the broader spectrum . In this sense, color is not a property of electromagnetic radiation, but a feature of visual perception by an observer . Furthermore, there is an arbitrary mapping between wavelengths of light in the visual spectrum and human experiences of color . Although most people are assumed to have the same mapping, the philosopher John Locke recognized that alternatives are possible, and described one such hypothetical case with the "inverted spectrum" thought experiment . For example, someone with an inverted spectrum might experience green while seeing' red' (700 nm) light, and experience red while seeing' green' (530 nm) light . Synesthesia (or ideasthesia) provides some atypical but illuminating examples of subjective color experience triggered by input that is not even light, such as sounds or shapes . The possibility of a clean dissociation between color experience from properties of the world reveals that color is a subjective psychological phenomenon . </P> <P> The Himba people have been found to categorize colors differently from most Euro - Americans and are able to easily distinguish close shades of green, barely discernible for most people . The Himba have created a very different color scheme which divides the spectrum to dark shades (zuzu in Himba), very light (vapa), vivid blue and green (buru) and dry colors as an adaptation to their specific way of life . </P> <P> Perception of color depends heavily on the context in which the perceived object is presented . For example, a white page under blue, pink, or purple light will reflect mostly blue, pink, or purple light to the eye, respectively; the brain, however, compensates for the effect of lighting (based on the color shift of surrounding objects) and is more likely to interpret the page as white under all three conditions, a phenomenon known as color constancy . </P> <P> Many species can see light with frequencies outside the human "visible spectrum". Bees and many other insects can detect ultraviolet light, which helps them to find nectar in flowers . Plant species that depend on insect pollination may owe reproductive success to ultraviolet "colors" and patterns rather than how colorful they appear to humans . Birds, too, can see into the ultraviolet (300--400 nm), and some have sex - dependent markings on their plumage that are visible only in the ultraviolet range . Many animals that can see into the ultraviolet range, however, cannot see red light or any other reddish wavelengths . For example, bees' visible spectrum ends at about 590 nm, just before the orange wavelengths start . Birds, however, can see some red wavelengths, although not as far into the light spectrum as humans . It is an incorrect popular belief that the common goldfish is the only animal that can see both infrared and ultraviolet light; their color vision extends into the ultraviolet but not the infrared . </P>

Which receptor in the eye is responsible for perceiving color