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