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