Rainbow-free 3-colorings of Abelian Groups

A 3-coloring of the elements of an abelian group is said to be rainbow--free if there is no 3-term arithmetic progression with its members having pairwise distinct colors. We give a structural characterization of rainbow--free colorings of abelian groups. This characterization proves a conjecture of Jungi\'c et al. on the size of the smallest chromatic class of a rainbow-free 3-coloring of cyclic groups.