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)(14,18)(15,21)(19,25)(22,27) involution — undirected(5,7,8,12)(6,9,10,11)(14,19)(15,22)(17,24)(18,25)(20,23)(21,27)(2,4)(7,12)(9,11)(13,14,17,19,16,18,24,25)(15,23,22,28,21,20,27,26)(6,10)(9,11)(14,18)(19,25)(20,23)(26,28) involution — undirected(13,15,24,27,16,21,17,22)(14,20,25,28,18,23,19,26)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.