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