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