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