One vertex per element, one color per generator, with an edge from x to x·s.
(1,2)(3,4)(5,6)(7,9)(8,10)(11,12)(13,14)(15,23)(16,19)(17,22)(18,21)(20,24)(25,28)(26,27) involution — undirected(2,4)(5,7,8,11)(6,9,10,12)(14,19)(15,24)(16,17)(20,28)(21,22)(25,26)(13,15,16,24,18,26,17,25)(14,20,19,27,21,28,22,23)(6,10)(9,12)(14,21)(19,22)(20,28)(23,27) involution — undirectedA 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.