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