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