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