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