Line an 8x8-inch baking dish with parchment paper, leaving some overhang for easy removal later.

In a medium saucepan over low heat, combine the white chocolate chips and sweetened condensed milk. Stir continuously until melted and smooth.

Remove the saucepan from heat and stir in the vanilla extract and salt.

Divide the melted fudge mixture evenly into three separate bowls.

Add a few drops of red food coloring to one bowl, blue to another, and yellow to the last. Stir each bowl until the colors are well combined.

Drop spoonfuls of each colored fudge into the prepared baking dish, alternating colors as you go.

Use a toothpick or skewer to swirl the colors together gently, creating a tie-dye effect.

Refrigerate the fudge for at least 2 hours or until firm.

Once set, lift the fudge out of the dish using the parchment paper and cut into squares.