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