  We study the interplay of the chiral and the color superconducting phase
transitions in an extended Nambu--Jona-Lasinio model with a multi-quark
interaction that produces the nonlinear chiral-diquark coupling. We observe
that this nonlinear coupling adds up coherently with the \omega^2 interaction
to produce the chiral-color superconductivity coexistence phase or cancel each
other depending on its sign. We discuss that large coexistence region in the
phase diagram is consistent with the quark-diquark picture for the nucleon
whereas its smallness is the prerequisite for the applicability of the
Ginzburg-Landau approach.
