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