| In this theory of strong interactions
the term color has nothing to do with the colors of the everyday
world but represents instead a special quantum property of quarks.
The colors red, green, and blue are ascribed to quarks, and their
opposites, minus-red, minus-green, and minus-blue, to antiquarks.
According to QCD, all combinations of quarks must contain equal
mixtures of these imaginary colors so that they will cancel out
one another, with the resulting particle having no net color.
A baryon, for example, always consists of a combination of one
red, one green, and one blue quark. The property of color in
strong interactions plays a role analogous to an electric charge
in electromagnetic interactions. Charge implies the exchange
of photons between charged particles. Similarly, color involves
the exchange of massless particles called gluons among quarks.
Just as photons carry electromagnetic force, gluons transmit
the forces that bind quarks together. Quarks change their color
as they emit and absorb gluons, and the exchange of gluons maintains
proper quark color distribution. |