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