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