I’m not suggesting that “it’s all a dream” but color is only the interpretation we give to different wavelengths of light. Is there a reason that a photon whose squiggles are 400 nanometers long should look violet, while the same photon slowed down to a wavelength of 570 nanometers should have the “opposite” color, yellow? If there is a connection, it is so remote as to appear arbitrary, and philosophers are still arguing about it.
However that debate plays out, we have the raw data (wavelength) and a very different interpretation (color).
Astonishingly, we are unconscious of the raw data. A child could stare all day at a cherry and a lime and have no way to tell you whether the red or the green had the shorter wavelength. In fact, if you were to ask him the question, he wouldn’t even know what you’re talking about. How amazing is that?
We invent (?) color to interpret the very different phenomenon of wavelength, and then we take the further step of assigning emotional states to colors. In some cases, the reason is clear: Black conveys doom because scary things do happen in the dark. In others, the assignment is arbitrary: Red means “danger” to an American, but “good luck” to the Chinese.
So the next time you’re bored and restless at a stoplight, maybe you’ll use the moment to marvel with me at how a wavelength of 650 nanometers came to mean “stop.”