One vertex per element, one color per generator, with an edge from x to x·s.
(1,2,3,4)(5,6)(7,20)(8,26)(9,33)(10,37)(11,18)(12,39)(13,19)(14,22)(15,29)(16,35)(17,36)(21,40)(23,42)(24,51)(25,49)(27,45)(28,59)(30,46)(31,63)(32,56)(34,44)(38,41)(43,55)(47,62)(48,61)(50,53)(52,64)(54,66)(57,67)(58,65)(60,68)(5,7,9,34,11,38,10,23,13,25,36,22,12,24,35,55)(6,14,16,49,39,42,17,41,19,44,37,20,18,43,33,51)(8,27,28,60,30,21,29,57,32,58,62,53,31,54,61,52)(15,45,46,64,59,66,26,50,48,65,63,67,47,40,56,68)(5,8,9,28,11,30,10,29,13,32,36,62,12,31,35,61)(6,15,16,46,39,59,17,26,19,48,37,63,18,47,33,56)(7,21,22,52,38,58,55,60,25,54,34,57,24,27,23,53)(14,40,20,50,42,45,51,67,44,66,49,68,43,65,41,64)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.