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