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