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