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)(25,26,30,32)(27,35,36,40)(28,37,39,33)(29,34,31,38)(1,3)(2,5)(4,7)(6,8)(9,11,13,19)(10,14,15,17)(12,20,21,18)(16,24,23,22)(26,32)(27,36)(33,37)(34,38)(2,6)(3,7)(25,27,29,37,30,36,31,33)(26,28,38,40,32,39,34,35)(10,15)(14,17)(16,23)(22,24)(25,28,30,39)(26,33,32,37)(27,34,36,38)(29,40,31,35)(3,7)(5,8)(9,12,13,21)(10,16,15,23)(11,18,19,20)(14,22,17,24)(25,29,30,31)(26,34,32,38)(27,37,36,33)(28,35,39,40)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.