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