Color charge

Colour charge is a property of quarks and gluons that is related to the particles' strong interactions in the theory of quantum chromodynamics (QCD). The "colour charge" of quarks and gluons is completely unrelated to the everyday meanings of color and charge. The term colour and the labels red, green, and blue became popular simply because of the loose analogy to the primary colours. Shortly after the existence of quarks was proposed by Murray Gell-Mann and George Zweig in 1964, Moo-Young Han and Yoichiro Nambu introduced a hidden internal degree of freedom in which quark wave functions were antisymmetric, thus solving the spin-statistics problem of the Gell Mann-Zweig quark model. Han and Nambu initially designated this degree of freedom by the group SU(3)', but it was referred to in later papers as "the three triplet model." One feature of the model (which was originally preferred by Han and Nambu) was that it permitted integrally charged quarks, as well as the fractionally charged quarks initially proposed by Zweig and Gell-Mann. Somewhat later, in the early 1970s, Gell-Mann, in several conference talks, coined the name "Color" to describe the internal degree of freedom of the three triplet model, and advocated a new field theory, designated as "Quantum Chromodynamics" (QCD) to describe the interaction of quarks and gluons within hadrons. In Gell-Mann's QCD, each quark and gluon had fractional electric charge, and carried what came to be called "Color Charge" in the space of the Color degree of freedom. In quantum chromodynamics (QCD), a quark's colour can take one of three values or charges: red, green, and blue. An antiquark can take one of three anticolors: called antired, antigreen, and antiblue (represented as cyan, magenta, and yellow, respectively). Gluons are mixtures of two colours, such as red and antigreen, which constitutes their colour charge. QCD considers eight gluons of the possible nine colour–anticolor combinations to be unique; see eight gluon colours for an explanation.