Hi, Steve. I really like old barns, especially old German-inspired full-sized Wisconsin dairy barns. Anyway, back to your question.(posted 9643 days ago)In Europe, 200 years ago, it was common to seal the wood on at least the weathered sides with oil, such as linseed oil, to make the structure last longer. It IS true that some rich farmer added blood from slaughter to tint his oil red, and there was the first red barn.
This became a status symbol, and an indication of doing a proper job, since the oil was a sealant. As that became the ideal, and the recognizable standard, people became accustomed to red barns. The notion came with immigrants to the U.S., and when Sherwin Williams started making paint for the first time in the 1800's, the line of paints was three different shades of red. The standard remained, until whitewash became cheaper, and thus a spread of white barns took over. In the last century, more barns were painted white than red.
(I'm partial to the old red ones)
Interestingly, down South in the U.S. there are a number of very old barns that have never been painted, and have held up well because of mild climate. Another thing we don't see much in the U.S. is the round or gazebo style barn, but they were popular for a short time. Well, this is more information than you asked for, sorry.
So, now you see why we have old red barns, and white farm houses. This still holds true around where I live.