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