No fix that Iv'e found . Black face can be even worse .
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Several ways to clean oxidation off anaodized aluminum. (which is what you face panel is)
I would take OFF the faceplate, and do the cleaning carefully acrosss the entire face. So if it changes the appearance a bit, it will be evenly colored.
If you try to just do a tiny bit, it will probably still look different. And trying to do the cleaning around the knobs etc, will also leave a pattern in the finish.