Yes the metal will grey as the finish wears however its never complete there are always some of the darker blue spots that remain. When worn I've observed that it still retains a slighty mottled look as opposed to a uniform grey.
There are no-drill scope mounts for Kragrifles available. If there were 2 slots cut into the stock at the top on either side of the receiver ring it might have had one of those installed hence the reason for the Buehler.