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