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