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