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