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)(13,14,18,22)(15,20,24,27)(16,21,17,19)(23,28,25,26)(5,6)(7,11)(8,10)(9,12)(14,19)(15,23)(16,17)(20,27)(21,22)(24,25) involution — undirected(2,4)(5,7,8,12)(6,9,10,11)(7,12)(9,11)(13,15,18,24)(14,20,22,27)(16,23,17,25)(19,26,21,28)(6,10)(9,11)(13,16,18,17)(14,21,22,19)(15,23,24,25)(20,28,27,26)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.