Combine white chocolate chips and sweetened condensed milk in a small saucepan.

Melt over low heat, stirring constantly, until mixture is smooth and completely melted.

Stir in Skittles.

Pour into an 8-inch square pan lined with parchment paper.

Squirt one drop of each color food coloring in a different corner of the pan; use a knife to create swirls of color.

Refrigerate or freeze until firm.