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