If we have quarks with three colours, is there a simple gauge principle for such a system? Yes, we can see the three different colours as coordinates in a three dimensional "colour space". If we want to compensate rotations, we have to introduce 8 compensating fields, the gluons. The gauge theory we have achieved is called QCD (Quantum Chromo Dynamics).

Since we deduced QCD with QED as a model, many characteristics remain unchanged. But there are also differences. The colour field traps quarks and gluons inside particles, no matter how forcefully we try to extract them.

The fundamental Feynman diagram of strong interactions.
(q=quark and g=gluon)

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