While the original screws were case colored, most of the A4's out there have been rebuilt. And, rebuilt A4's will often have the base & screws parkerized. So, don't worry about that.

You really need to shim the base at the correct height BEFORE you attempt to mount the scope. The base should not be mounted without shims, as it is the generic Redfield Jr base was selected not because it was an exact fit, but because it was available. I suspect that military armorers made some kind of fixture so that the height of the base was consistent; the 330 series scopes do not have enough adjustment to compensate for being a lot out of alignment.

If you want, I could try to measure the base height for you, either with a micrometer, or maybe my set of spark plug feeler gauges.