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