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