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