For they become colourd by reflecting the Light of their own Colours more copiously, and that of all other colors more sparingly." (Opticks, Book I, Part II, Experiment 15)
Generally, colour vision is merely a physical ability of an organism or human being. A colour is perceived by the human eye as a combination of different wavelengths. The ability of humans to distinguish colours is an interesting question, which has been discussed by scientists for many years. Thus, a number of theories have been created. These theories will be discussed in the present paper.
According to Peter Gouras “color vision is an illusion created by the interactions of billions of neurons in our brain. There is no color in the external world; it is created by neural programs and projected onto the outer world we see. It is intimately linked to the perception of form where color facilitates detecting borders of objects” (Gouras , 1969).
There are two main theories explaining the ability of humans to distinguish colours: trichromatic colour vision and opponent process theory. The researches devoted to the development of trichomatic colour vision were initiated in 18th century by Thomas Young. This scientist claimed that human vision is caused by interaction of three different kinds of photoreceptor cells. Later on, claims of this scientist were experimentally proven by Hermann von Helmholtz. Therefore it was proven that a human required 3 wavelengths in order to distinguish all colours.
More detailed discussion of this theory requires additional facts. There are 3 kinds of cones in the retina of the eye; each of these 3 cones has various photosensitive pigments. Different kind of pigment is sensitive to different light wavelength. Cones are of three different types: long, medium and small, ranging from 560 nm to 420 nm respectively (Dacey,