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