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