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