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