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