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What does colour charge mean in quantum chromodynamics?

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subatomic particle The Large Hadron Collider (LHC), the world's most powerful particle accelerator. At the LHC, located underground in Switzerland, physicists study subatomic particles.

In quantum chromodynamics (QCD), colour charge is a fundamental property of quarks that acts as the source of the strong force, which binds quarks together to form hadrons such as protons and neutrons.21

While the term is an analogy to the primary colours of light—specifically red, green, and blue—it has no connection to colour in the everyday sense. This property was introduced to resolve a paradox involving the Pauli exclusion principle, which otherwise forbids identical fermions from occupying the same quantum state.23

Key aspects of colour charge include:
* Neutrality: Nature only permits the existence of "colour-neutral" or "white" particles. In baryons, this is achieved by combining one quark of each of the three colours. In mesons, a quark and an antiquark combine, where the anticolour neutralizes the colour.21
* Force Carriers: Quarks interact by exchanging gluons. Unlike the photons of quantum electrodynamics, which are electrically neutral, gluons themselves carry colour charge, allowing them to interact with one another.23
* Confinement: Because gluons carry colour, the strong force prevents quarks from being isolated, leading to their permanent confinement within composite particles.21