Linked from
The 30 pages that link to Graph coloring, each with the reason it gives.
Complete graphRelated: A complete graph on n vertices requires n distinct colors.
Vertex (graph theory)Related: A vertex's color is constrained by the colors of its neighbors.
Odd cycleRelated: An odd cycle requires three colors for a proper vertex coloring.
Induced subgraphRelated: Coloring behavior on induced subgraphs helps characterize perfect graphs.
Graph homomorphismRelated: A proper coloring is exactly a homomorphism to a complete graph.