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