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