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