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