  Rapidity gaps between two hard jets at the Tevatron have been interpreted as
being due to the exchange of two gluons which are in an overall color-singlet
state. We show that this simple picture involves unitarity violating
amplitudes. Unitarizing the gluon exchange amplitude leads to qualitatively
different predictions for the fraction of $t$-channel color singlet exchange
events in forward $qq$, $qg$ or $gg$ scattering, which better fit Tevatron
data.
