  We apply Ginzburg-Landau theory to determine BCS pairing in a
strongly-coupled uniform superfluid of three-flavor massless quarks in flavor
equilibrium. We elucidate the phase diagram near the critical temperature in
the space of the parameters characterizing the thermodynamic potential terms of
fourth order in the pairing gap. Within the color and flavor antisymmetric
channel with zero total angular momentum, the phase diagram contains an
isoscalar (IS) color-antitriplet phase and a color-flavor-locked (CFL) phase,
reached by a second order transition from the normal state, as well as states
reached by a first order transition. We complement the general Ginzburg-Landau
approach by deriving the high-density asymptotic form of the Ginzburg-Landau
free energy from the weak-coupling gap equation. The dynamically-screened,
long-range color magnetic interactions are taken into account in solving the
gap equation. We find that in the limit of weak coupling, the IS phase is less
favorable near the transition temperature than the CFL phase. In view of the
fact that deconfined quark matter must be color charge neutral, we incorporate
the constraint of overall color neutrality into the Ginzburg-Landau theory and
the gap equation. This constraint yields a disparity in the chemical potential
between colors and reduces the size of the gap, in the presence of the
anisotropy of the order parameters in color space. In comparison with the case
in which there are no chemical potential differences between colors and hence
the superfluid generally has nonzero net color charge, we find that while the
constraint of color neutrality has only negligible effects on the gap in the
weak coupling regime, it appreciably destabilizes the IS phase in the strong
coupling regime without affecting the CFL phase.
