Effects of subleading color in a parton shower

Parton shower Monte Carlo event generators in which the shower evolves from hard splittings to soft splittings generally use the leading color (LC) approximation, which is the leading term in an expansion in powers of 1/N 2 ,where Nc =3 is the number of col-ors. In the parton shower event generator Deductor, we have introduced a more general approximation, the LC+ approximation, that includes some of the color suppressed contri-butions. In this paper, we explore the differences in results between the LC approximation and the LC+ approximation. Numerical comparisons suggest that, for simple observables, the LC approximation is quite accurate. We also argue that for gap-between-jets cross sections neither the LC approximation nor the LC+ approximation is adequate.