Hello, everyone. What do the blue and pink color the rust indicator shown mean? Let say, the mixture of potassium hexacyanoferrate(III) and phenolphthalein is the rust indicator. And we use to detect the rusting of an iron nail. And the result is: the tip, head region of the nail appear blue color; the straight region appears pink color. Is that the blue region shows Fe2+ ions formed? And, the pink shows hydrogen ions present? But, even it shows these ions are present, what does it mean? The blue area is rusting? And the pink area no rusting? Confused :( please help!!