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