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