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