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