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