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