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