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