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