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