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