Positive dependence for colored percolation

Abstract

For uniform random 4-colorings of graph edges with colors a,b,c,d, every two colors form a 1/2-percolation, and every two overlapping pairs of colors form independent 1/2-percolations. We show joint positive dependence for pairs of colors ab, ac and ac, and joint negative dependence for pairs of colors ab, ac and bc. The proof is based on a generalization of the Harris--Kleitman inequalities. We apply the results to crossing probabilities for the colored bond and site percolation, and to colored critical percolation that we also define.