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