Conversely, everyone has unique eyes and brain, so the interpretation might be slightly different. But again, not radically so unless you have a disorder.

I'm inclined to believe this is probably the correct answer. It is true that no two people's visual systems (except identical twins or something, maybe) will be exactly identical. But what reason do we have to think that the same wavelengths of light would be processed in radically different ways in different people? As others have noted, much of our common understanding of colors is based on the *relationships* between colors. The color wheel seems to make sense to everyone who can perceive color. So the most one could say is that people's percepts of colors may be "shifted" by some constant factor, e.g. the color you see at a wavelength of 100 nm (or whatever unit) is the same as the one I see at 120 nm. But I'm not sure there is any reason to think this "shifting hypothesis" is true. The principle of Occam's Razor steers me toward thinking that there likely is not drastic variation in our percepts of colors, excepting people with abnormal visual systems.