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