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