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