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