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