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