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