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