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