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