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