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