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