  In a two-flavor color superconductor, the SU(3)_c gauge symmetry is
spontaneously broken by diquark condensation. The Nambu-Goldstone excitations
of the diquark condensate mix with the gluons associated with the broken
generators of the original gauge group. It is shown how one can decouple these
modes with a particular choice of 't Hooft gauge. We then explicitly compute
the spectral density for transverse and longitudinal gluons of adjoint color 8.
The Nambu-Goldstone excitations give rise to a singularity in the real part of
the longitudinal gluon self-energy. This leads to a vanishing gluon spectral
density for energies and momenta located on the dispersion branch of the
Nambu-Goldstone excitations.
