Must be a classic thread on this...

So if I find a set the needs the black shiny or the mat silver "re-matted"

Where is the classic thread on this?

It's gotta be there.
it might help in your search if you spell 'Fuchs' the way it's spelled...

The "matte silver" is the original anodise.
Anodise is not a DIY process - this is why we don't talk about it much here.
You might be able to simulate it with some kind of matte dulling spray or powder coat, but the dulling sprays tend to be temporary or yellow upon UV exposure, making you wish they were temporary. I don't even want to think about dealing with getting powder coat off an aluminum wheel...

You can remove the anodise to polish the rim, but putting it back requires chemicals and equipment outside the scope of most.

Repainting the black involves either a BIG vat of black paint (factory method) or careful use of flexible masking tape.

Here's my DIY thread

Well that didn't work - Do a search under my name and "Re-finished Fuchs myself RSR style"