I've never had linseed oil damage or remove any bluing or c/color.
I've use the junk in the jumbo can from the DIY stores and in the more recent years linseed sold for Artists Oil Painting.
The latter really does dry, something the former didn't like to do w/o some very lengthy waits dispite the 'boiled' on the lable.
I use it sparingly and don't consider it a stock finish in itself anyway. A micro-thin top coat over the filled wood is about it.
It does make it's way onto the metal when applied to an assembled gun and I make no attempt to avoid it.
I also have used it as a first oil coating on newly rust blued or browned bbls and parts. Never a problem damaging the metal finish.
