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