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