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