Color charge

In particle physics, color charge is a property of quarks and gluons which are related to their strong interactions in the context of quantum chromodynamics (QCD). This has analogies with the notion of electric charge of particles, but because of the mathematical complications of QCD, there are many technical differences. The "color" of quarks and gluons have nothing to do with the visual perception of color, but is a whimsical name for a property which has almost no manifestation at distances above the size of an atomic nucleus.

Red, blue and green

One can say that a quark's color can take three values: "red", "green", or "blue"; and that an antiquark can take on three "anticolors", sometimes called "antired", "antigreen" and "antiblue" (occassionally represented as cyan, magenta and yellow). In the same vein it can be said that gluons are mixtures of two colours: for example red-antigreen, and this constitutes their color charge. Also it is further stated that there are eight gluons, leaving one to figure out where the ninth one went. In this language, the answer is that one particular combination: the (red-antired)+(blue-antiblue)+(green-antigreen) is actually colourless and hence does not need to be considered any more. This is about as far as one can push this language. Further elaboration requires a little bit of background which the next sections build and use. One should read them along with the companion article on coupling constants.

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