25 Pretty graph colouring problems

Even if there is nothing more to say about the 4-colour-problem, there are very many easily formulated unsolved graph colouring problems left. We have selected a list of 25 pretty problems. If a class of graphs is closed under minors (deletions and contractions), is the maximum chromatic number of graphs in the class equal to the largest order of a complete graph in the class? Assume that all vertex-critical induced proper subgraphs of a vertex-critical graph G are complete. Is G complete, an odd cycle or an odd cycle complement? What is the chromatic number k of the graph whose vertices are all points in the plane, with two vertices joined by an edge when they are of distance 1? It is known that 4 k 7.