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