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)(27,31)(28,32)(29,30)(33,35)(34,39)(36,40)(37,38)(3,7)(5,8)(11,15)(13,16)(17,19,20,23)(18,21,22,24)(26,30)(31,33)(32,38)(39,40)(1,2,4,6)(3,5,7,8)(9,11,12,15)(10,13,14,16)(17,19)(18,21)(20,23)(22,24)(25,26)(27,33)(28,32)(29,30)(31,35)(34,40)(36,39)(37,38)(1,2)(3,5)(4,6)(7,8)(17,18)(19,21)(20,22)(23,24)(25,27,29,35)(26,31,30,33)(28,36,37,34)(32,40,38,39)(1,3)(2,5)(4,7)(6,8)(9,10)(11,13)(12,14)(15,16)(17,18)(19,21)(20,22)(23,24)(25,28,29,37)(26,32,30,38)(27,34,35,36)(31,39,33,40)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.