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