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