Natasha Geiling details the history of the movie theater snack:
Before the Great Depression, most popcorn sold was a white corn variety–yellow corn wasn’t widely commercially grown, and cost twice as much as the white variety. Movie vendors, however, preferred yellow corn, which expanded more when it popped (creating more volume for less product) and had a yellowish tint that belied a coating of butter. People became accustomed to the yellow popcorn and would refuse to buy the white variety at markets, requesting the kind that looked like “the popcorn at the movies.” Today, white popcorn accounts for 10 percent of commercially grown popcorn; yellow popcorn takes up almost the rest of the commercial market (with some color varieties, like blue and black, grown in negligible amounts).
The Dish 