Jello
Sour cream

Choose colors and flavors of Jello as desired. I use 5 colors to make a rainbow: purple, green, yellow, orange and red.

For each color: Dissolve Jello in 1 cup boiling water. Divide in half. To one half, add 2 tablespoons cold water. Pour into 9"x13" pan and refrigerate 1/2 hour. To the second half add 1/3 cup sour cream and keep at room temperature. When clear Jello is set, carefully pour sour cream mixture over it and refrigerate 1/2 hour. Repeat for each color. The hardest part of this recipe is finding a flat bottomed pan.