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