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