  We study the color-dependent confining forces between two quarks by the
quenched lattice simulations of Coulomb gauge QCD. The color-singlet and
color-antitriplet instantaneous potentials yield attractive forces. The ratio
of the string tensions obtained from them is approximately 2 and have little
volume dependence. Meanwhile, the color-octet and color-sextet channels give a
minor contribution for two-quark system. We finally find that the infrared
self-energy of the color-nonsinglet channels diverges in the infinite volume
limit; however, the degree of the divergence on the finite lattice can be
understood in terms of color factors.
