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