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