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