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