Some history for you, older people like Moreluck probably remember white margarine !
United States:
As early as 1877, the first United States (U.S.) states had passed laws to restrict the sale and labeling of margarine. By the mid-1880s, the U.S. federal government had introduced a tax of two cents per pound, and manufacturers needed an expensive license to make or sell the product. Individual states began to require the clear labeling of margarine. The color bans, drafted by the butter lobby, began in the dairy states of New York and New Jersey. In several states, legislatures enacted laws to require margarine manufacturers to add pink colorings to make the product look unpalatable, but the Supreme Court struck down New Hampshire's law and overruled these measures in Collins v. New Hampshire, 171 U.S. 30 (1898). Some localities required restaurants using margarine to post signs reading "Artificial Butter Used Here".
By the start of the 20th century, eight out of ten Americans could not buy yellow margarine, and those that could had to pay a hefty tax on it.
Bootleg colored margarine became common, and manufacturers began to supply food-coloring capsules so that the consumer could knead the yellow color into margarine before serving it.
Nevertheless, the regulations and taxes had a significant effect: the 1902 restrictions on margarine color, for example, cut annual U.S. consumption from 120,000,000 to 48,000,000 pounds (54,000 to 22,000 t).
The long-running rent-seeking battle between the margarine and dairy lobbies continued:
In the U.S., the Great Depression brought a renewed wave of pro-dairy legislation; the Second World War, a swing back to margarine.
Post-war, the margarine lobby gained power and, little by little, the main margarine restrictions were lifted, the most recent states to do so being Minnesota in 1963 and Wisconsin in 1967. Some unenforced laws remain on the books