Interesting discussion about color vision on dirty:
“…Modern science explains color vision as follows:
In the human eye there are two types of light-sensitive cells (photoreceptors): highly sensitive rods and less sensitive cones. Rods function under relatively low light conditions and are responsible for the mechanism of night vision, but at the same time, they provide only a neutral color perception of reality, limited to the participation of white, gray, and black colors. Cones operate at higher levels of illumination than rods. They are responsible for the daytime vision mechanism, the distinguishing feature of which is the ability to provide color vision.
In the retina of the human eye, there are three types of cones, the sensitivity peaks of which are in the red, green, and blue parts of the spectrum. The spectral sensitivity curves of the three types of cones overlap partially, which facilitates the phenomenon of metamerism.
In many cases, the theory corresponds well with practice. For example:
1) Monochromatic yellow in the spectrum is located between red and green, thus equally illuminating the “red” and “green” cones. A similar effect can be achieved by mixing monochromatic red and green light; they will also equally illuminate the “red” and “green” cones, and we will see yellow, although there are no wavelengths of yellow in the light at all.
2) As the wavelength increases beyond red, the sensitivity of “red” cones decreases, we perceive this as a reduction in the brightness of red. We do not see infrared.
But there are points that do not agree with the theory, and which I could not find answers to:
1) The sensitivity curves of “red” and “green” cones are quite close and overlap significantly, because of which, for example, monochromatic red light, apart from “red” cones, will partially illuminate the “green” ones. Theoretically, instead of pure red or green, we should see red-yellow or green-yellow. However, in practice, we see pure colors. Why?
2) Why, when mixing blue and red, do we see purple? After all, in the spectrum, purple is between blue and ultraviolet, not between red and blue.
3) Why, when the wavelength decreases after blue, do we generally see purple? According to the theory, we should just see a reduction in the brightness of blue.
In trying to find answers, I only found the phrase that modern science has not yet fully explored the phenomenon of color vision.
(…)
It is not possible to just throw together such an algorithm, because the brain is not a von Neumann machine, but a very complex self-learning neural network. And what you get from the eye is very different from what you actually see. At a minimum, initially from the eye you get an image that is upside down and distorted, like from a ‘fish-eye’ lens type. Furthermore, it also has holes. Starting from the blind spot and ending with dead cells on the retina, which everyone has. These holes are filled in by the brain at its discretion. Further, the eyes are constantly making small movements at a high frequency, i.e., the real image trembles and floats. This too is filtered by the brain. And approaching the subject of colors directly—colors only really exist in the brain. In objective reality, there are no colors, there is only light of different wavelengths. Evolutively, it so happened that the brain supplements the signals perceived from the retina cells with additional information, i.e. essentially tags them. This apparently evolved to perceive the world more detailedly, obviously giving some advantage to primates. Most likely the ability to visually distinguish ripe fruits from unripe ones. And these very tags are colors—green, red, purple, etc. However, these colors are very incorrectly related to real optics since their purpose is strictly utilitarian. Moreover, we cannot even be sure that we see colors the same way. What your brain perceives as red, someone might see as blue, yet we have agreed to call that color “red” and everyone calls it that. Google “qualia”. Because of all described, there are several dozen different color perception disorders, and not all of them are related to changes in the retina cells.” (https://science.dirty.ru/voprosy-o-tsvetovom-zrenii-1272066/)
Hi, I'm Rauf Aliev. 