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