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