"The early farmers that settled in New England didn't have much extra money to spend on paint, so most of their barns remained unpainted. By the late 1700s, farmers looking to shield their barns' wood from the elements began experimenting with ways to make their own protective paint.
A recipe consisting of skimmed milk, lime and red iron oxide created a rusty-colored mixture that became popular among farmers because it was cheap to make and lasted for years. Farmers were able to easily obtain iron oxide the compound that lends natural red clay its coppery color from soil. Linseed oil derived from flax plants was also used to seal bare wood against rotting, and it stained the wood a dark coral hue."