Step 1Heat oven to 350 degrees. Cook the macaroni in plenty of rapidly boiling lightly salted water until tender, about 12 minutes. Drain.
Step 2Melt the butter in a saucepan over medium heat and whisk in the flour. Cook, stirring, until the raw flour smell goes away, 2 to 3 minutes. Stir in the milk and cook until smooth. Add 3 1/2 cups Cheddar, seasoned salt, white pepper and food coloring and stir until the cheese melts, about 5 minutes. Stir in the macaroni.
Step 3Pour into an 8-inch baking dish, sprinkle with the reserved 1/2 cup of Cheddar and cover the dish with aluminum foil. Bake 30 minutes, then remove the foil and bake until lightly browned on top, about 30 minutes more.