One vertex per element, one color per generator, with an edge from x to x·s.
(1,2)(3,5)(4,6)(7,8)(9,10,12,14)(11,13,15,16)(17,18)(19,23)(20,21)(22,24)(26,30)(27,33)(32,36)(35,39)(4,8)(6,7)(17,18)(19,23)(20,21)(22,24)(25,26,29,30)(27,31,33,34)(28,32,37,36)(35,38,39,40)(2,3)(6,7)(18,21)(22,23)(25,26)(27,34)(28,36)(29,30)(31,33)(32,37)(35,38)(39,40) involution — undirected(1,3,5,2)(4,7,8,6)(9,10)(11,13)(12,14)(15,16)(17,18)(19,22)(20,21)(23,24)(25,27)(26,31)(28,35)(29,33)(30,34)(32,38)(36,40)(37,39)(1,4,5,8)(2,6,3,7)(9,11,12,15)(10,13,14,16)(17,19,20,24)(18,22,21,23)(25,28,29,37)(26,32,30,36)(27,35,33,39)(31,38,34,40)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.