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