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