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