There are only two types of color cells in the human body.
Retinal cones have three kinds of light-sensitive pigments, red, green and blue, each of which absorbs light at different wavelengths to produce color vision. If the light – sensitive pigments in the cones are abnormal or incomplete, this results in abnormal color vision. The color lens is designed according to the principle of chromatography. Through the antagonism of the spectrum, the brightness of the color can be changed so as to improve the sensitivity of color resolution. However, the feeling of wearing the color blind glasses is different from that of normal people.
Red and green color perception are actually very similar colors.
So if a person lacks a red or green cone, that person’s color vision spectrum is completely different from the average person’s.
It’s not that they don’t see red and green, it’s that they don’t appear at the same time and it’s hard to tell them apart.
So with a filter lens, one eye filters out the red or green wavelengths, they can tell the traffic lights when they’re driving. For example, always see, the other always see not. But this also has a defect, that is, only when the two eyes are looking at the traffic lights to distinguish, otherwise, only one side of the vision, is unable to distinguish, so, need to face up to the traffic lights.