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