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