Around 1877, the first states in the US had passed laws restricting the sale of margarine. The reason for this was because there was a powerful butter lobby trying to get the federal government to restrict the sale of margarine in one way or another. It got so bad that eventually the federal government passed a tax of 2¢ per pound of margarine.
Most states passed laws requiring clear labeling of margarine. Most extreme, however, was the many states that required margarine manufacturers to use pink coloring in the manufacturing. The reason for this was to make the product look unpalatable. The Supreme Court had to come in and overturn these laws! In the meantime, however, 80% of people could not buy yellow margarine.
Manufacturers even started selling coloring capsules so people could recolor the margarine yellow at home. Did you know that there had been such a hard fought war between butter and margarine?