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