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