It turns deep salmon when rubbed with iron salts (Ferrous sulfate).
Olsen, C. (1938) Experiments with different quantities of iron salts given to maize in water culture.
The color came from coating paper with light-sensitive iron salts.
Then the paper is chemically developed in a process that replaces the iron salts with platinum.
It helps in the availability of clean water by reducing the salinity and the presence of iron salts.
This color is degraded by the presence of iron salts.
The paper has brownish "fox marks" caused by the accumulation of iron salts due to moisture.
In "doubly fortified salt", both iodide and iron salts are added.
Next, the solutions of lithium salts and iron salts are added to this mixture.
It contains plant tannins mixed with iron salts present in the fermented mud.