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