  Using data from e+e- annihilation into hadrons, taken with the OPAL detector
at LEP at the Z pole between 1991 and 1995, we performed a simultaneous
measurement of the colour factors of the underlying gauge group of the strong
interaction, CF and CA, and the strong coupling, alpha(s). The measurement was
carried out by fitting next-to-leading order perturbative predictions to
measured angular correlations of 4-jet events together with multi-jet related
variables. Our results,
  CA = 3.02 +/- 0.25 (stat.) +/- 0.49 (syst.),
  CF = 1.34 +/- 0.13 (stat.) +/- 0.22 (syst.), alpha(s)(M_Z) = 0.120 +/- 0.011
(stat.) +/- 0.020 (syst.), provide a test of perturbative QCD in which the only
assumptions are non-abelian gauge symmetry and standard hadronization models.
The measurements are in agreement with SU(3) expectations for CF and CA and the
world average of alpha(s)(M_Z).
