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