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