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