The Ladies’ Home Journal, March 1948

From early on in the 20th century, coloured margarine was banned in the US and Canada because butter manufacturers were afraid it would harm their business. They wanted butter to be yellow and margarine to stay white. While it was illegal for businesses to colour their margarine yellow, this ad shows one company’s clever work around: included was a small capsule which you’d pop and eventually your margarine would turn butter-yellow!