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