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