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