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