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