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)(11,15)(12,13)(14,16)(18,21)(22,24)(25,26)(27,33)(28,32)(29,30)(31,35)(34,40)(36,39)(37,38) involution — undirected(3,7)(6,8)(9,10)(11,15)(12,13)(14,16)(19,23)(22,24)(26,30)(31,33)(32,38)(39,40) involution — undirected(2,5)(6,8)(10,13)(14,15)(17,18,20,21)(19,22,23,24)(25,26)(27,33)(28,32)(29,30)(31,35)(34,40)(36,39)(37,38)(1,2)(3,6)(4,5)(7,8)(9,10)(11,14)(12,13)(15,16)(17,18)(19,22)(20,21)(23,24)(25,27,29,35)(26,31,30,33)(28,36,37,34)(32,40,38,39)(1,3,4,7)(2,6,5,8)(9,11,12,16)(10,14,13,15)(17,19,20,23)(18,22,21,24)(25,28,29,37)(26,32,30,38)(27,34,35,36)(31,39,33,40)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.