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