Delta-conjecture (1978)

consider a complete graph (V; E_1, \dots, E_d) each edge of which is colored by one of d colors such that there exists a triangle \Delta colored in three pairwise distinct colors. Then, in each chromatic component (V, E_i), i = 1, \dots, d, one can choose a maximal independent vertex-set such that the intersection of the obtained d sets is empty.