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