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