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