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