My brother-n-law, nephew and cousin always fight over this...They all want to get the corners where the cheese crusts up, they say that's the best part. I call it "Me and Granny's" because she gave me the recipe and I added my own touches over the years...
I like to prep first; Preheat oven at about 300 degrees; shredd your colby and divide it (half/half); beat your eggs and mix with evaporated milk; measure out your butter and 2% milk and set aside in fridge.
In a large pot add about 8 cups of water; about a teaspoon of salt and about 1/4 cup of cooking oil and bring to a rolling boil. Add elbow macaroni from the 8 oz bag and from the kraft box; stir to make sure the noodles are not sticking to pot; return to a boil stirring occasionally until noodles are tender. Drain and rinse noodles in a collander with warm water, then rrinse again with cold water to stop the cooking process.
place noodles in a large mixing bowl and add the cheese sauce from the kraft deluxe, the can of cheddar cheese soup, and the cup of milk. Stir until ingredients are well combined and cheese soup is coating the noodles.
in a large casserole dish or glass baking dish (13x9) spread half the pasta mixture, sprinkle lightly with salt (if desired) and place about four pats of butter around this layer. Next, cover the layer with half of the mozzarella cheese and half of the colby cheese; repeat the steps for the second layer.
next, take the evaporated milk mixture and pour over your macaroni evenly (make sure that it is not too much that it will overflow in the oven). You can cover this loosely with foil (I like to bake mine uncovered) and bake at 300 degrees for about 45 minutes (please note that the time is not exact, it may be a little more or a little less depending on your oven). You want the cheese to be bubbly and golden brown. I like mine a little darker because I like the taste of crusted cheese.
Please note that I really do not measure anything when I cook so feel free to play around with this to suit your taste.