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