One vertex per element, one color per generator, with an edge from x to x·s.
(1,2)(3,4)(5,6)(7,9)(8,10)(11,12)(13,14,18,21)(15,22,24,27)(16,20,17,26)(19,25,28,23)(5,7)(6,9)(8,11)(10,12)(13,15,16,25,18,24,17,23)(14,19,26,27,21,28,20,22)(2,4)(7,11)(9,12) involution — undirected(7,11)(9,12) involution — undirected(6,10)(9,12)(13,16,18,17)(14,20,21,26)(15,23,24,25)(19,27,28,22)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.