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