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