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