An e-star is a complete bipartite graph K e 1, . An e-star system of order n S n > 1, ( )chromatic number, colouring, decomposition, star system, unique colouring A M S C L A S S I F I C A T I O N 05B30; 05C51; 05C15 1 1 ∪ ⩽⩽ DARIJANI AND PIKE | 531 How to cite this article: Darijani I, Pike DA. Colourings of star systems. J Combin Des.