Is all color composed of primary colors?
Not exactly. We have 3 types of cone cells that contribute to our perception of color, so all color can be described in terms of the relative stimulation of these cells. However, the physical phenomena that cause our percpetion of color are not necessarily composed of three primary colors. How do we reconcile these two thoughts? Let’s consider the primary colors green and red. We can talk about pure green light, which is typically around 510 nm, and pure red light, which is typically around 650 nm. If we mix these together in approximately equal proportions, we will get the perception of yellow. However, the perception of yellow, is different from the physical phenomenon of pure yellow light, which happens to have a wavelength of about 580 nm, and which also happens to have the perception of yellow. (Not surprisingly, 580 this is the average of 510 and 650.) There are infinitely many combinations of color that can cause the perception of yellow light without including any actual yellow
