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