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