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