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