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