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