Coloring squares of graphs via vertex orderings

We provide upper bounds on the chromatic number of the square of graphs, which have vertex ordering characterizations. We prove that G(2) is (3 Delta - 2)-colorable when G is a cocomparability graph, (Delta + mu)-colorable when G is a strongly orderable graph and (Delta + 1)-colorable when G is a dually chordal graph, where Delta(G) is the maximum degree and mu(G) = max{vertical bar N-G(x) boolean AND N-G(y)vertical bar: x, y is an element of V (G)} is the multiplicity of the graph G. This improves the currently known upper bounds on the chromatic number of squares of graphs from these classes.