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