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