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)(15,23)(16,22)(17,21)(18,20)(19,26)(24,28)(25,27) involution — undirected(1,2)(3,4)(6,9)(10,12)(13,15,17,26)(14,19,21,23)(16,25,18,24)(20,27,22,28)(14,20)(15,24)(16,18)(21,22)(25,26)(27,28) involution — undirected(2,4)(5,7,8,11)(6,10,9,12)(14,20)(15,24)(16,18)(21,22)(25,26)(27,28)(6,9)(10,12)(13,16,17,18)(14,20,21,22)(15,25,26,24)(19,27,23,28)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.