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