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