Line an 8x8-inch baking dish with parchment paper, making sure it hangs over the edges for easy removal later.

Place the white chocolate chips, sweetened condensed milk, butter, and a pinch of salt into a medium saucepan. Warm over low heat, stirring frequently, until the mixture is fully melted and smooth.

Divide the melted mixture evenly into three separate bowls. Leave one bowl plain, tint the second with red food coloring, and the third with green. Stir each bowl until the color is fully blended.

Spoon the mixtures into the prepared pan, alternating between the three colors to create layers. Use a knife or skewer to gently swirl the colors together for a marbled effect.

Sprinkle holiday sprinkles evenly over the top while the fudge is still soft.

Place the pan in the refrigerator and chill for 3-4 hours, or until the fudge is firm.

Once set, lift the fudge out of the pan using the parchment paper and cut into 1-2-inch squares.

Serve right away or store in an airtight container until ready to enjoy.