List coloring and diagonal coloring for plane graphs of diameter two.

Let G be a maximal plane graph of diameter at most two. Let χl(G) and χd(G) denote the list chromatic number and the diagonal chromatic number of G, respectively. In this paper, we study the structure of G and show the following results: (1) χl(G) ≤ 4; and (2) χd(G) ≤ 9, and χd(G)=9 if and only if G is a specific graph on nine vertices.