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