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