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