Sorry, elk, but I have never heard of a way to remove one layer of paint without affecting another. However, one way to solve your problem is to get a chip of your blue paint and have it color analyzed.
If it is milk paint it will be pretty flat. One way to get this effect is to mix some talcum powder in with your paint. Cheapest talcum powder you can get at any drug store works great but be sure to mix well and keep it mixed. If it has any gloss at all, there could have been varnish put over the milk paint at some time.
Todays paints are a lot better than any 200 year old paints, particularly the higher quality lines. In your position, I would look at something like Benjamin Moore's top line. The cost is twice what home center paint costs but you should not need a lot and the ease of applying and durability makes it more than worth while. Milk paint is still available and while it is OK for something like furniture, I would not use it for something like woodwork that can take a pretty good beating.
Hope this helps and good luck. Henry in MI
If you have just 2 or 3 coats of paint or varnish on your woodwork, I would use Citristrip for the paint removal but if you have a lot of paint buildup, you might have to go with something like Peel Away.