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