One vertex per element, one color per generator, with an edge from x to x·s.
(2,5)(6,8)(9,10,12,13)(11,15,16,14)(17,18)(19,20)(21,24)(22,23)(25,26)(27,31)(28,34)(29,37)(30,33)(32,38)(35,40)(36,39)(10,13)(14,15)(17,19)(18,22)(20,24)(21,23)(25,27,30,28)(26,31,33,34)(29,35,38,36)(32,39,37,40)(9,10)(11,14)(12,13)(15,16)(17,20)(18,23)(19,24)(21,22)(25,28,30,27)(26,31,33,34)(29,36,38,35)(32,39,37,40)(1,2)(3,6)(4,5)(7,8)(9,10)(11,15)(12,13)(14,16)(17,20)(18,19)(21,22)(23,24)(25,26)(27,34)(28,31)(29,32)(30,33)(35,40)(36,39)(37,38) involution — undirected(1,3,4,7)(2,6,5,8)(9,11,12,16)(10,14,13,15)(17,19)(18,22)(20,24)(21,23)(25,29)(26,32)(27,35)(28,36)(30,38)(31,39)(33,37)(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.