One vertex per element, one color per generator, with an edge from x to x·s.
(2,5)(6,8)(9,10,12,14)(11,15,16,13)(19,23)(22,24)(25,26)(27,33)(28,32)(29,30)(31,34)(35,40)(36,39)(37,38)(9,11)(10,13)(12,16)(14,15)(18,21)(22,24)(26,30)(27,34)(32,38)(35,36) involution — undirected(9,10,12,14)(11,13,16,15)(17,18)(19,22)(20,21)(23,24)(25,27)(26,31)(28,36)(29,34)(30,33)(32,40)(35,37)(38,39)(1,2)(3,6)(4,5)(7,8)(9,11)(10,13)(12,16)(14,15)(25,26)(27,31)(28,32)(29,30)(33,34)(35,39)(36,40)(37,38) involution — undirected(1,3,4,7)(2,6,5,8)(9,10)(11,13)(12,14)(15,16)(17,19,20,23)(18,22,21,24)(25,28,29,37)(26,32,30,38)(27,35,34,36)(31,39,33,40)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.