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