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