It is illegal to sell margarine colored yellow to imitate butter.

The Law Explained

In a massive protectionist move for the state's dairy farmers, it was once a crime to dye margarine yellow. The law forced grocers to sell margarine in its natural, unappetizing pale gray color, sometimes including a separate capsule of yellow food coloring for housewives to mix at home. The dairy lobby fought fiercely to keep fake butter looking as terrible as possible.