  We consider the first quantised approach to quantum field theory coupled to a
non-Abelian gauge field. Representing the colour degrees of freedom with a
single family of auxiliary variables the matter field transforms in a reducible
representation of the gauge group which - by adding a suitable Chern-Simons
term to the particle action - can be projected onto a chosen fully
(anti-)symmetric representation. By considering F families of auxiliary
variables, we describe how to extend the model to arbitrary tensor products of
F reducible representations, which realises a U(F) "flavour" symmetry on the
worldline particle model. Gauging this symmetry allows the introduction of
constraints on the Hilbert space of the colour fields which can be used to
project onto an arbitrary irreducible representation, specified by a certain
Young Tableau. In particular the occupation numbers of the wavefunction - i.e.
the lengths of the columns (rows) of the Young Tableau - are fixed through the
introduction of Chern-Simons terms. We verify this projection by calculating
the number of colour degrees of freedom associated to the matter field. We
suggest that, using the worldline approach to quantum field theory, this
mechanism will allow the calculation of one-loop scattering amplitudes with the
virtual particle in an arbitrary representation of the gauge group.
