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