Coke has always been brown. Caramel was originally used for coloring, and though the (secret) formula has changed over the years, caramel, which imparts the brown color we know, is still used to give the cola its appearance.

There is currently an urban legend stating Coca-Cola's color was originally green, and this is incorrect. The company at one time used green bottles, and thus the idea was started. The product has always had its standard brown color.