The reason most barns are painted red has to do with the chemistry of dying stars, Smithsonian explains, as well as the economy. Basically, barns are red because red paint is cheap, and it’s cheap because it’s plentiful.
Red paint is plentiful due to the bounty of red ochre, a compound made of iron and oxygen that absorbs yellow, green and blue light. And this is where dying stars come into the picture. Smithsonian lets Yonatan Zunger, a Google employee, explain the science behind this everyday sight.