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