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