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