Help Color 1890 5 Cents Grant

Is the dark color of the stamp on the left normal or is it defective?

Looks like oxidation has darkened the stamp on the left.

As with all your "help me with color...." stamps, this might be lead poisoning.
Use a hydrogen peroxide solution and brush or soak your stamps with the solution. Usually degraded stamps will return to their original color (more or less).

Thank you very much

While I agree that you have a color changeling, I would not recommend that you try to "restore" it unless or until you know what shade of brown it started with. Otherwise you run the risk of creating something that never was printed as you now see it. Mind you that there were several shades of unlisted trial colors for this stamp, so knowing where to stop is a gamble.

What you see now is quite uniform and is interesting in its own right inasmuch as it occurred naturally. Once you hit it with the H2O2 you can remove "naturally" from the description. Why destroy it?

I agree with you Essayk. I'm not going to change it because the stamp is generally in good condition.