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