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