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