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