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