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