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