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