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