Coca-Cola and the color red go together like peanut butter and jelly, milk and cookies, or tacos and Tuesdays. After all, we would recognize that iconic red label (or maybe even that Coca-Cola yellow cap) anywhere. Over 130 years ago, Coca-Cola was sold in barrels at American drug stores and pharmacies. Alcohol was distributed in the same way. But while alcohol was taxed at the time, soft drinks were not. So, the Coca-Cola Company began painting its barrels red in order to help customs and tax officials distinguish them from barrels of booze.

Source: Reader's Digest