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