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