  When rapidity gaps in high-$p_T$ dijet events are identified by energy flow
in the central region, they may be calculated from factorized cross sections in
perturbative QCD, up to corrections that behave as inverse powers of the
central region energy. Although power-suppressed corrections may be important,
a perturbative calculation of dijet rapidity gaps in ${\rm p}\bar{\rm p}$
scattering successfully reproduces the overall features observed at the
Tevatron. In this formulation, the average color content of the hard scattering
is well-defined. We find that hard dijet rapidity gaps in quark-antiquark
scattering are not due to singlet exchange alone.
