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