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