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