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