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