Keith Novak: the author of the book is Oliver Sacks. A neurologist by training, his books are an interesting mix of the purely physical ("body is a machine that can be fixed") and the more esoteric ("There's more 'twixt heaven and earth"). At least, that is how I read them. Very interesting.
The man who became colourblind was particularly interesting - if memory serves he didn't want to go back to "normal" (whatever that means, no offence meant etc.) since he had gained a new appreciation of the world around him. The lack of colour made him appreciate other things - and more than just the gradations. At least, that's how I remember the story.
Colour perception is a frequent discussion point where I work (our lunch discussions are rather infamous by now 😎 ). Is what we perceive as red, actually red? Ultimately it's just electromagnetic radiation, of a wavelength (~680 nm) our eyes can detect and our brains process into a colour. We can't see wavelengths longer than about 700 nm, but suppose we could. Would there be another red? Is colour like sound, then. An "A" in music is defined as 440 Hz, but that has changed in the course of history. After all, "A" is just a name (I grew up calling it "la"). If 440 Hz is A, then so is 880 Hz, 1760 Hz etc. - each doubling is an octave. Hence: if 650 nm light is red, what about 1300 nm or 2600 nm? We can't see them, but what if we could...
Incidentally, a friend of mine on a bored afternoon used this trick on the Cosmic Background Radiation. Take the wavelength of it and keep doubling it until you end up in the visible spectrum. It turns out that the universe is dark green!
Perhaps more interestingly - is my green as green as your green? Even if you have "normal" (save caveats as before) colour vision, how do I know that you think my green coat is as green as I think it is? Or: I take a picture and use a certain film to achieve a certain effect, say Velvia vs. Portra. But if you perceive colour different from me, is that even meaningful? And from that: how would you test this? It's a fun thought experiment and we've yet to decide whether there is an observer-independent way of doing this.
I'm rambling. This is how our lunchtime conversations go (except we don't always keep it this clean 😉 😀 ).
Doctor Zero
Edit: And this is all without considering perceiving colours individually or next to each other. The human eye is very sensitive in comparing two colours next to each other, but much less good if it's shown one first and then another. Lots of optical illusions are based on this.
