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