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