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