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