Do we all see different colors?

How do we see different colors?

• Which colors are our eyes most sensitive to? Which colors are the "primary colors of light"? Is their primariness a feature of the colors themselves, or of the human eye? When we see yellow light, does is necessarily mean that yellow photons are entering our eyes?

• Answer:

  The eye has two different types of photoreceptors, rods and cones. Rods are responsible for low-light vision, which is just black and white. Cones are responsible for color vision. There are three types of cones, one for blue, one for green, and one for red. They're often designated L, M, and S based on the wavelength of light, as blue is short wavelength, green is medium wavelength, and red is long wavelength (relative wavelengths in the visible light spectrum). As for what colors our eyes are most sensitive to? Well, this figure says it all, and breaks it down by cone types: http://upload.wikimedia.org/wikipedia/commons/1/1e/Cones_SMJ2_E.svg As for "primary colors of light", that doesn't make much sense without saying primary with respect to WHAT. The color of light is dependent on the wavelength/frequency/energy (if you know 1 of those 3, you know the other 2) of the light. And, color only applies to things we can see--most of the light spectrum is outside our range of vision. Plus, primary colors usually refers to art, and the "primary colors" there are picked for usefulness in terms of mixing them to yield other colors, and nothing more. When we see yellow light, we perceive the yellowness. In reality, a photon (actually, many photons) with a wavelength of approximately 570 nanometers has interacted with the M and L cone cells to produce an electrochemical impulse that our brain merely interprets as being yellow. In this sense, color is only in our minds.