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