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)(11,15)(12,20)(13,17)(14,18)(16,19)(21,23)(22,24)(25,26,29,32)(27,30,35,39)(28,31,36,40)(33,37,34,38)(1,3,5,8)(2,6,7,4)(9,11,14,13)(10,15,18,17)(12,19,21,22)(16,23,24,20)(25,27,29,35)(26,30,32,39)(28,33,36,34)(31,37,40,38)(9,12,14,21)(10,16,18,24)(11,19,13,22)(15,23,17,20)(27,33)(28,36)(30,37)(31,40)(34,35)(38,39)(1,4,5,6)(2,3,7,8)(10,17)(11,13)(15,18)(16,20)(19,22)(23,24)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.