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