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