This is something that has always interested me. Humans perceive just under one octave of light but several octaves of sound. When we hear tones an octave apart we can easily recognize their similarities as well as their differences: a high C is different than a low C but they are both still a C!

It seems reasonable to suppose that the same thing would happen with colors if we could ever find (or design) a human sensitive to more than one octave of light. Even now there are qualities of both redness and blueness in the highest-frequency color we can see, namely violet, on the verge of the next higher octave.

I have also experienced synaesthesia myself, thanks to being in college in the 1960s and enjoying some incredible LSD trips. Hearing colors and seeing sounds is a common effect under the influence of psychedelic substances, and I value the experience. There is nothing like a live demonstration of how flexible our brains really are to keep one humble about what we think "reality" is!