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