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