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