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