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