  We show that color ferromagnetic phase of quark matter is energetically more
favored than color superconducting phases in neutron stars. Namely, increasing
baryon density in neutron stars transforms nuclear matter into the quark matter
of the color ferromagnetic phase. Further increase of the density makes the
quark matter take the color superconducting phases. We find that a critical
mass of the neutron star with such an internal structure is about
$1.6M_{\odot}$. We stress that analysis of gluon dynamics is crucial for
exploring dense quark matter.
