We employ a bispinor gap equation to study superfluidity at nonzero chemica
l potential, mu not equal 0, in two- and three-color QCD, exploring the gap
's sensitivity to the nature of the quark-quark interaction. The two-color
theory, QC(2)D, is an excellent exemplar; the order of truncation of the qu
ark-quark scattering kernel K has no qualitative impact, which allows a str
aightforward elucidation of the effects of mu when the coupling is strong.
in the three-color theory the rainbow-ladder truncation admits diquark boun
d states, a defect that is eliminated by an improvement of K. The corrected
gap equation describes a superfluid phase that is semiquantitatively simil
ar to that obtained using the rainbow truncation. A model study suggests th
at the width of the superfluid gap and the transition point in QC(2)D provi
de reliable quantitative estimates of those quantities in QCD. [S0556-2813(
99)07112-5].