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