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