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