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