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