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