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