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