Preheat oven to 350 and spray a 13x9x2 inch pan(or even a 15 inch pan is better) with cooking spray
Put cooked macaroni into dish. Add cubed butter, velveeta, colby, cheddar, jack, salt, pepper, sugar and incorporate well.
Take sour cream and dolop it around. Beat eggs and add whole milk and evaporated milk. Pour this over the entire dish.
Sprinkle mild cheddar over entire top of dish. Bake for 45-55 minutes, or until top is melted (the longer you cook, the browner the top will be. This is a matter of taste. Serve hot. But you can also freeze this and microwave another day, and it's almost just as good.