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)(13,14)(15,22)(16,17)(18,21)(19,24)(20,23)(25,26)(27,28) involution — undirected(1,2,3,4)(13,15,23,28,18,25,16,24)(14,19,17,26,21,27,20,22)(6,10)(9,11)(13,16,18,23)(14,17,21,20)(15,24,25,28)(19,26,27,22)(7,12)(9,11)(13,17,23,21,18,20,16,14)(15,22,28,19,25,26,24,27)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.