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