In a bowl, melt the white chocolate chips and sweetened condensed milk in 30-second increments. Stir until combined, then add in the vanilla extract and salt.
Divide the mixture into three bowls. Then add a little red food coloring into one bowl, and stir. Do the same with the second bowl. Add a little blue food coloring, and stir.
Alternate pouring the three colors into the baking pan. Repeat. Then top with sprinkles and allow it to set for 3 hours or overnight in the fridge before slicing and enjoying!