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