Red barns aren't as ubiquitous here in western North Carolina as in other parts of the country. Unpainted barns were the norm for a long time. Still, that iconic red barn of children's books and country-themed calendars tugs at many of us. Our own red barn was unpainted for many years . . . and then John bought a spray painter.
I love the weathered gray of many old barns. But the way that red pops against a green background is nice. And the paint adds protection to the wood.
A little on line research reveals that the red paint may have originated in New England in the late 1700s when thrifty farmers, seeking to protect their barns' wood from the weather began experimenting with ways to make their own protective paint.
One mixture 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. Another preservative was linseed oil, derived from flax seed -- and flax, grown for linen, was a common crop. It was found that adding rust to the linseed oil created a nice rust-red finish to the wood.