I don't know exactly what is meant by color when used as in the original
question but I want my students to understand that there is no particular
wavelength of electromagnetic radiation that is perceived as white and therefore
no wavelength we would call white light. I want them to understand that white
is something that your brain makes up when it overloads on visible wavelengths
coming from a common source. The eye sends a message that says there is some
blue light coming from over there along with some green. Some red is mixed in
too. Perhaps some purple or even a bit of yellow. Now your brain having
received all of these varying messages from the optic nerve says something
like... Blue, green, red, yellow...what should I do with all of this???? I
think I'll make something up. How about white. The only place in the universe
that white exists is in your brain.
As to the question whether we all perceive the same thing when we see what our
brain calls white, I am with Jim Green. I wonder. Perhaps if I were inside
your head and experienced what you do when you think white I might perceive
sour?? I don't think there is any way to find out.
--
Cliff Parker
Never express yourself more clearly than you can think. -- Niels Bohr