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