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