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