Sweden and the Nordic countries are known for its many red houses. This is the story behind them.
The paint is called Falu Red (”Falu rödfärg”). Falun is a Swedish town that used to have a copper mine. Falu Red is made from byproducts of the mining process.
In the 16th century it was fashionable to use copper on roofs of rich people's houses in continental Europe. In Sweden we mostly built wooden houses, but the Swedish King, Johan III, wanted to have the look of a copper roof so he had the roof of the castle painted in ”rust led” (Falu Red). That started the trend of painting roofs and houses red in Sweden. At first only rich people could afford it. Nowadays it is very common on all sorts of wooden houses.
As a side note, the company that makes the original Falu Red, Stora Kopparberg Bergslags AB, was the worlds first stock company when it sold shares of the company in the 13th century. The company still lives, more than 700 years after it was founded.
The mine, Falun Mine, has been closed for mining for many years, but today it is a museum and UNESCO world heritage site well worth a visit.
Mining started in Falun in the 10th century and continued for 1,000 years, until it closed in 1992. In its heyday the mine produced 2/3 of the copper needed in all of Europe. It funded several of Swedens wars in the 16th century. The Thirty Years' War was one of them. Sweden hasn't always been a peaceful country. :-)