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