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