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