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