They do not react with each other, but if you add only a small droplet of sulfuric acid to the solution Prussian blue will be formed and some deadly hydrogen cyanide gas may be realeased. It is because that the one complex in very acidic conditions decompose to iron(III or II) ion and six cyanide ions. Because of that very acidic conditions must be avoided working with these two salts.

Here I've mixed them to show that nothing happens.