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)(28,36)(29,30)(32,38)(33,34)(35,40)(37,39)(1,3,5,7)(2,4,6,8)(9,10)(11,12)(13,14)(15,16)(18,21)(22,24)(26,30)(27,33)(32,36)(35,37)(2,6)(3,7)(10,14)(11,15)(17,18,20,21)(19,22,23,24)(25,27,29,33)(26,31,30,34)(28,37,38,35)(32,40,36,39)(1,2)(3,4)(5,6)(7,8)(9,11,13,15)(10,12,14,16)(25,26)(27,34)(28,32)(29,30)(31,33)(35,40)(36,38)(37,39)(1,4)(2,3)(5,8)(6,7)(9,12)(10,15)(11,14)(13,16)(17,19,20,23)(18,22,21,24)(25,28)(26,32)(27,35)(29,38)(30,36)(31,39)(33,37)(34,40)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.