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