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