  We study the effect of color superconductivity and neutrino trapping on the
deconfinement transition of hadronic matter into quark matter in a protoneutron
star. To describe the strongly interacting matter a two-phase picture is
adopted. For the hadronic phase we use different parameterizations of a
non-linear Walecka model which includes the whole baryon octet. For the quark
matter phase we use an $SU(3)_f$ Nambu-Jona-Lasinio effective model which
includes color superconductivity. We impose color and flavor conservation
during the transition in such a way that just deconfined quark matter is
transitorily out of equilibrium with respect to weak interactions. We find that
deconfinement is more difficult for small neutrino content and it is easier for
lower temperatures although these effects are not too large. In addition they
will tend to cancel each other as the protoneutron star cools and deleptonizes,
resulting a transition density that is roughly constant along the evolution of
the protoneutron star. According to these results the deconfinement transition
is favored after substantial cooling and contraction of the protoneutron star.
