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