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