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