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