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