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