Between the input (wavelength) and output (colour), what occurs? How do we receive 650nm, for example, and interpret it as red? What even is red? What is colour, really?
In: Physics
There is a peculiar property of chemicals that a few of them react only with specific wavelengths of light.
Think about pigments that are used to dye clothes. A red dye absorbs all colors except red. You can make a dye in reverse that only absorbs red color; you have made a dye that can detect the color red if you hook it up to a neuron. When it absorbs red light, a little signal is created. So you have a cell that detects light of a certain wavelength, which we call red in English. The eyes also detects blue and yellow.
In day to day life, you do not experience monochromatic color, meaning a pure single wavelength such as lasers produce. A laser red looks fake or not as rich a red, because we are used to colors being a mixture of many wavelengths. In this aspect, color is a rich experience where there are seemingly unlimited possibilities for slight variation. A single wavelength stimulates our eye color receptors and then our brain figure out what it is most like. This is how we assign ROYGBIV to the monochromatic color spectrum. Red stimulates mostly the red receptor. Yellow stimulates yellow. Orange stimulates both red and yellow, and so forth.
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