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