  We suggest a scenario where the three light quark flavors are sequentially
deconfined under increasing pressure in cold asymmetric nuclear matter as
found, e.g., in neutron stars. The basis for our analysis is a chiral quark
matter model of Nambu--Jona-Lasinio (NJL) type with diquark pairing in the
spin-1 single flavor (CSL), spin-0 two flavor (2SC) and three flavor (CFL)
channels. We find that nucleon dissociation sets in at about the saturation
density, n_0, when the down-quark Fermi sea is populated (d-quark dripline) due
to the flavor asymmetry induced by beta-equilibrium and charge neutrality. At
about 3n_0 u-quarks appear and a two-flavor color superconducting (2SC) phase
is formed. The s-quark Fermi sea is populated only at still higher baryon
density, when the quark chemical potential is of the order of the dynamically
generated strange quark mass. We construct two different hybrid equations of
state (EoS) using the Dirac-Brueckner Hartree-Fock (DBHF) approach and the EoS
by Shen et al. in the nuclear matter sector. The corresponding hybrid star
sequences have maximum masses of, respectively, 2.1 and 2.0 M_sun. Two- and
three-flavor quark-matter phases exist only in gravitationally unstable hybrid
star solutions in the DBHF case, while the Shen-based EoS produce stable
configurations with a 2SC phase-component in the core of massive stars. Nucleon
dissociation via d-quark drip could act as a deep crustal heating process,
which apparently is required to explain superbusts and cooling of X-ray
transients.
