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)(14,19)(15,21)(16,25)(17,24)(20,22)(23,28)(26,27) involution — undirected(5,7,9,8)(6,10,12,11)(14,20)(15,21)(16,25)(17,24)(19,22)(23,27)(26,28)(1,2,3,4)(5,7,9,8)(6,11,12,10)(13,14,21,27,17,23,16,20,18,22,25,28,24,26,15,19)(5,8,9,7)(6,11,12,10)(14,22)(19,20)(23,26)(27,28)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.