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