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