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