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