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