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