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