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)(11,20)(12,17)(13,18)(14,29)(15,19)(16,23)(21,32)(22,33)(24,30)(25,31)(26,34)(27,36)(28,35)(37,40)(38,39) involution — undirected(1,3)(2,5)(4,7)(6,8)(9,11,14,21,15,23,13,24)(10,16,18,32,19,20,29,30)(12,25,27,37,28,22,26,38)(17,33,34,40,35,31,36,39)(2,6)(5,8)(11,21)(13,14)(16,30)(18,29)(20,32)(22,38)(23,24)(25,37)(26,27)(31,40)(33,39)(34,36) involution — undirected(3,7)(5,8)(9,12,15,28)(10,17,19,35)(11,22,23,25)(13,27,14,26)(16,31,20,33)(18,36,29,34)(21,37,24,38)(30,39,32,40)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.