Key limes are the pink flamingos of Florida food, and they are a celebrated part of local color. Key West, Florida, is famous for its fabulous key lime pie, one of America's best-loved regional dishes. Aficionados of key lime pies argue endlessly about the proper way to make one. Graham-cracker or pastry crust? Meringue on top or whipped cream, or neither? Cooked or uncooked filling? The one thing that they do agrees on is that under no circumstances should you ever add green food coloring. The filling of authentic key lime pie is a light yellow.