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