  The combined effect of the repulsive vector interaction and the positive
electric chemical potential on the chiral phase transition is investigated by
considering neutral color superconductivity. Under the charge-neutrality
constraint, the chiral condensate, diquark condensate and quark number
densities are obtained in two-plus-one-flavor Nambu-Jona-Lasinio model with the
so called Kobayashi-Maskawa-'t Hooft term. We demonstrate that multiple chiral
critical-point structures always exist in the Nambu-Jona-Lasinio model within
the self-consistent mean-field approximation, and that the number of chiral
critical points can vary from zero to four, which is dependent on the
magnitudes of vector interaction and the diquark coupling.
