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