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