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