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