We show that, in two space dimensions, the full many-Fermion interacti
on has the structure of a vector model at every energy scale. The <<co
lours>> arise from a decomposition of the Fermi circle into sectors of
length set by the energy scale. These sectors play an essential role
in summing up the complete perturbation series. The three-dimensional
vertex is intermediate between vector and matrix models. In any number
of dimensions the reduced interaction is a vector model.