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