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