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