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