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