1. The problem statement, all variables and given/known data Describe how the colour degree of freedom of the quarks can be used to explain the fact that, at electron energies of about 20GeV the cross section for e+e- annihilation into hadrons is of the order 4 times the cross section for e+e- -> mu+mu-. 2. Relevant equations None given 3. The attempt at a solution But I thought that colour degrees of freedom related to hadrons, not leptons, so how does it fit into an electron positron annihilation.