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)(19,23)(22,24)(26,30)(27,33)(28,36)(38,40) involution — undirected(1,3,5,4)(2,6,7,8)(9,10)(11,15)(12,16)(13,14)(18,21)(22,24)(26,30)(28,36)(31,34)(35,39)(3,4)(6,8)(10,14)(12,15)(17,18,20,21)(19,22,23,24)(25,26,29,30)(27,34,33,31)(28,32,36,37)(35,40,39,38)(1,2)(3,6)(4,8)(5,7)(9,11)(10,15)(12,14)(13,16)(17,19,20,23)(18,22,21,24)(25,27)(26,31)(28,35)(29,33)(30,34)(32,38)(36,39)(37,40)(1,4,5,3)(2,6,7,8)(9,12,13,15)(10,16,14,11)(25,28)(26,32)(27,35)(29,36)(30,37)(31,38)(33,39)(34,40)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.