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