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