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