Color charge

Color charge is a property of quarks and gluons that is related to the particles' strong interactions in the theory of quantum chromodynamics (QCD). Like electric charge, it determines how quarks and gluons interact through the strong force; however, rather than there being only positive and negative charges, there are three "charges", commonly called red, green, and blue. Additionally, there are three "anti-colors", commonly called anti-red, anti-green, and anti-blue. Unlike electric charge, color charge is never observed in nature: in all cases, red, green, and blue (or anti-red, anti-green, and anti-blue) or any color and its anti-color combine to form a "color-neutral" system. For example, the three quarks making up any baryon universally have three different color charges, and the two quarks making up any meson universally have opposite color charge. The "color charge" of quarks and gluons is completely unrelated to the everyday meaning of color, which refers to the frequency of photons, the particles that mediate a different fundamental force, electromagnetism. The term color and the labels red, green, and blue became popular simply because of the loose but convenient analogy to the primary colors.