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