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