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