On the colorings of outerplanar graphs Original Research Article

In this paper, we have studied seven colorings of outerplanar graphs. Two main conclusions have been proved: if G is an outerplanar graph without cut vertex and Δ(G) ⩾ 6, then (i) χef(G) = Δ(G), and (ii) χvef(G) = Δ(G) + 1, where χef and χvef are the edge-face chromatic number and the entire chromatic number of G, respectively, and Δ(G) is the maximum degree of vertices of G.