  We analyse the nucleation of quark matter droplets under protoneutron star
conditions. We adopt a two-phase framework in which the hadronic phase is
described through a non-linear Walecka model and the just deconfined matter by
the MIT bag model including color superconductivity. Surface tension and
curvature energy are calculated self-consistently within the MRE formalism. We
impose flavour conservation during the transition, which means that the just
deconfined quark droplet is transiently out of equilibrium with respect to weak
interactions. Our results show that trapped neutrinos slightly increase the
critical density for deconfinement and that color superconductivity
significantly decreases such density at low temperatures. We also show that the
nucleation rate is negligible for droplets larger than 100-200 fm and is huge
for smaller droplets provided that the temperature is low enough. We compare
our results with previous calculations using the Nambu-Jona-Lasinio model with
color superconductivity and the MIT bag model without color superconductivity.
We conclude that the deconfinement transition should be triggered
instantaneously when a density slightly larger than the bulk transition density
is reached at some layer of a protoneutron star. Since color superconductivity
lowers the transition density at low temperatures, the transition is likely to
occur after significant cooling in a massive enough protoneutron star.
