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