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