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