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