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