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