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