What is Colour vision?
'''Color vision''' is the capacity of an [[organism]] to distinguish objects based on the [[wavelength]]s (or [[frequency|frequencies]]) of the [[light]] they [[Reflection|reflect]], [[emit]], or [[Transmission|transmit]]. Color is a quality made by the [[brain|visual brain]] and so it is ''not'' a [[property]] of [[object]]s, despite what children are taught.<ref>If this is doubted, remember that there are animals which cannot see colors, or who only see one or two colors.</ref> The wavelength reflected from an object is the objective fact: it does not depend upon perception. A 'red' apple does not emit red light.<ref>{{Cite book|author=Wright, W.D. |title=The rays are not coloured [sic]: essays on the science and vision and colour [sic] |url=https://archive.org/details/raysarenotcolour0000wrig |publisher=Hilger |location=Bristol |year=1967 |isbn=0-85274-068-9 }}</ref> Rather, it simply absorbs all the [[frequency#Frequency of waves|frequencies]] of [[visible light]] shining on it except for a group of frequencies that are reflected. It is these frequencies which are seen or ''[[Perception|perceived]]'' as red. ==Mechanism== [[File:Eyesensitivity.svg|thumb|upright=1.25|Relative brightness sensitivity of the human visual system as a function of wavelength]] The [[spectrum|visible light spectrum]] ranges from about 380 to 740 nanometers. Colors of the [[spectrum]] such as red, orange, yellow, green, cyan, blue, and violet are in this range. These spectral colors do not refer to a single wavelength, but rather to a set of wavelengths: red, 625–740&nbsp;nm; orange, 590–625&nbsp;nm; yellow, 565–590&nbsp;nm; green, 500–565&nbsp;nm; cyan, 485–500&nbsp;nm; blue, 450–485&nbsp;nm; violet, 380–450&nbsp;nm. The nervous system derives color by comparing the responses to light from the several types of [[Cone cell|cone photoreceptors]] in the eye. These cone photoreceptors are sensitive to different portions of the [[vision|visible]] [[spectrum]]. For humans, the visible spectrum ranges approximately from 380 to 740&nb