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