A study of the particle multiplicity between jets with large rapidity separation has been performed using the D0 detector at the Fermilab Tevatron p¯p Collider operating at √s=1.8TeV. A significant excess of low-multiplicity events is observed above the expectation for color-exchange processes. The measured fractional excess is 1.07±0.10(stat)+0.25−0.13(syst)%, which is consistent with a strongly interacting color-singlet (colorless) exchange process and cannot be explained by electroweak exchange alone. A lower limit of 0.80% (95% C.L.) is obtained on the fraction of dijet events with color-singlet exchange, independent of the rapidity gap survival probability.Received 20 September 1995DOI:https://doi.org/10.1103/PhysRevLett.76.734©1996 American Physical Society