Cook pasta al dente according to package instructions.

While pasta is cooking, combine about 2 tablespoons of warm water and 1 to drops of food coloring in a large zip-top plastic bag.

Mix the dye and water together until well combined.

Repeat with however many additional colors you would like.

When pasta is finished cooking, drain and immediately rinse in cold water to stop the cooking process.

Transfer the pasta in even portions to the prepared zip top bags and seal.

Use your hands to carefully combine the pasta and food coloring, and then let each bag sit for at least 1 minute to soak up the color.

Then, one color at a time, transfer a bag of pasta back to the strainer and rinse with cold water to remove any extra food coloring.

Then transfer the pasta back to your original pot.

Repeat with the remaining colors of pasta.

Toss all of the colors of pasta together to combine the colors.

In a large saucepan, melt butter over medium heat.

Add the garlic and lower the heat to medium low and cook for 2 to 3 minutes. Do not brown.

Once the garlic has cooked, whisk in flour and cook until it begins to smell nutty and fragrant, about 45-60 seconds.

Whisk in milk and stock, and continue whisking vigorously until flour and butter have dissolved. Bring to sauce to a bubble and thicken, about 3-4 minutes.

Once sauce is thick, remove from heat and mix in mustard and cheddar cheese.

Stir until cheese is completely melted.