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