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