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