  Efficient methods for describing non abelian charges in worldline approaches
to QFT are useful to simplify calculations and address structural properties,
as for example color/kinematics relations. Here we analyze in detail a method
for treating arbitrary non abelian charges. We use Grassmann variables to take
into account color degrees of freedom, which however are known to produce
reducible representations of the color group. Then we couple them to a U(1)
gauge field defined on the worldline, together with a Chern-Simons term, to
achieve projection on an irreducible representation. Upon gauge fixing there
remains a modulus, an angle parametrizing the U(1) Wilson loop, whose
dependence is taken into account exactly in the propagator of the Grassmann
variables. We test the method in simple examples, the scalar and spin 1/2
contribution to the gluon self energy, and suggest that it might simplify the
analysis of more involved amplitudes.
