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