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