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