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