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