Which of the following is a stain for heart failure cells?

Heart failure cells, also called siderophages, are hemosiderin-containing macrophages in the alveoli of lung and these cell denote previous episodes of pulmonary edema due to left-sided heart failure. Hemosiderin is nothing else but stored iron granules. So, heart failure cells contain iron granules and thus will require a stain that is used for iron. Stain used for iron is Prussian blue reaction (Perl's iron stain)