One of my friends recently stated: "black is not a colour. It is the entire
Here is an answer I gave on February 10 2010. For your reductionist friend I would answer that the perception of black is positive - it is not a null perception, in some sense, but nor is it the perception of nothing, so that nothing (or Nothing, rather) looks black - presumably It doesn't look any colour. I also want to add that black is not in the spectrum, obviously, for what that is worth (nothing, actually) and that "black" and "dark" have different meanings. If you take a dimmer switch and gradually increase the light in a completely dark room, as the illumination goes up, the reds get redder, the greens greener, and amzaingly the blacks get blacker! What does this tell us?
From Feb 10 2012 This is a fairly frequent concern. The correct answer is that there is a sense of "colours" in which black and white are not colours (they are not chromatic colours) and a sense in which they are colours (they are achromatic colours). So if we count the achromatic colours (black, white and grey) as colours, then black and white are colours. (Brown is an interesting case, as it is a colour which is partially achromatic.) In the same way, we can ask whether zero and infinity are numbers. Usually they are treated as numbers, and they have their own mathematical symbols. We can manipulate them in calculations and so forth. But in another sense "zero" denotes the absence of a number, and so does the symbol for an infinite number. Q: "How many chickens were there in the kitchen?" A: "A number." Q: "What is the number?" A: "Zero"! Aristotle's view was that the smallest number is two, as one of something is not a number of somethings. "There were a number of people there." How many?" "One." In this sense two is the first crowd-like or milling number. One won't mill around. Logicians face the same difficulty in explaining that in their sense "some" means only "at least one".
The situation is that colours arrange themselves into three dimensions: saturation, hue, and brightness. Hue is colourfulness, the colourfulness of red, yellow, blue, green and so on, and colourfulness does not include black, white and grey. Colourfulness is the circling hue dimension at maximum saturation, and the achromatic colours lie in their own vertical dimension at the center of the solid whose surface is this colourfulness or saturation. White has zero saturation, and we make other pigments of various chromatic colours less saturated - paler - by mixing in white pigment. (It is an interesting question why this concept - paleness - has a "special relationship" only with white.)
So at the end of the day the fact is that in one way black and white behave as colours, and in another way they work to create diminutions and absences of colour. Wittgenstein was right (in his Remarks on Colour) to see a puzzling element of necessity, a necessity as hard as logical necessity, in these striking facts.