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