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