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