  Employing constraints derived from the microscopic theory of the strong
interaction, we estimate the zero-temperature phase structure of dense
isospin-asymmetric matter with two quark flavors. We find indications that
strong-interaction matter along trajectories relevant for astrophysical
applications undergoes a first-order phase transition from a
color-superconducting phase to an ungapped quark-matter phase when the density
is increased. Such a phase transition is found to be absent in
isospin-symmetric matter. Moreover, by taking into account constraints from
$\beta$-equilibrium, charge neutrality, and color neutrality, we provide an
estimate for the speed of sound in neutron-star matter. Notably, we observe
that the speed of sound in neutron-star matter exceeds the asymptotic value
associated with the noninteracting quark gas and even increases towards lower
densities across a wide range, in agreement with recent results for
isospin-symmetric matter. Considering results from studies based on chiral
effective field theory at low densities, our findings suggest the existence of
a maximum in the speed of sound for $n/n_0 \lesssim 10$, where $n_0$ is the
nuclear saturation density.
