Melt coloured wax into the holes.
Hadn't thought of that. I'm in Edinburgh next week where there is still some residual Goth pollution, so black candles should be relatively easy to find....
Thanks.
Decent m
rifle makers included blanking screws. My Mauser M96 Slide Bolt came with them fitted into the scope mounting holes for those who like to use iron sights. P-H also fitted them.

The ham shanks have no appreciation of the state of 'gunsmithing' here, of course plug screws are the 'best' but when your local plumber stares blankly at you what are you supposed to do eh?
Truth be told; not many actually know how to identify a thread anyhoo!