Some equitably 3-colourable cycle decompositions Original Research Article

Let G be a graph in which each vertex has been coloured using one of k colours, say c1,c2,…,ck. If an m-cycle C in G has ni vertices coloured ci, i=1,2,…,k, and |ni−nj|⩽1 for any i,j∈{1,2,…,k}, then C is equitably k-coloured. An m-cycle decomposition C of a graph G is equitably k-colourable if the vertices of G can be coloured so that every m-cycle in C is equitably k-coloured. For m=4,5 and 6, we completely settle the existence problem for equitably 3-colourable m-cycle decompositions of complete graphs and complete graphs with the edges of a 1-factor removed.