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)(17,18,20,21)(19,23,24,22)(25,26,30,28)(27,33,34,31)(29,36,37,32)(35,38,40,39)(9,10)(11,15)(12,13)(14,16)(18,21)(22,23)(27,34)(29,37)(31,33)(32,36) involution — undirected(10,13)(11,16)(17,19,20,24)(18,22,21,23)(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)(11,15)(12,13)(14,16)(17,19)(18,22)(20,24)(21,23)(25,28,30,26)(27,31,34,33)(29,36,37,32)(35,38,40,39)(1,3,4,7)(2,6,5,8)(9,11,12,16)(10,14,13,15)(17,18)(19,23)(20,21)(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.