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