It is one of those things once you hear it you cannot “unthink” it every time you think of it; like why do we call bacon bacon and cookies cookies when you cook bacon and bake cookies? Now, that is something you can unthink but that is not what I am going to make you think of. Why are barns red? In short: Rust! If you live in the South, tobacco barns are black for the purpose of heating and drying out the leaves but I am referring to classic livestock and other non-tobacco barns. Back before "Valspar paints" and "Home Depot", people, including farmers, used paint not for decoration but for utilitarian purposes. Rust is simply just oxidized iron; the oxidation turns the iron to a red rusty color. Since most everything made of metal left outside in the weather oxidizes, rust was very common on an old farm. That is not to say rust was not made in special places just for paint, it was. However, this common orange-red rust color paint was not just aesthetically pleasing it had real uses too. Rust was well known to kill fungi and other likens and mosses that could decay the wooden structure. Now whenever you see a red barn, you will think back to this article and know why red was all the rage back in the day and still carries on today.