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