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