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