Scoop out all the spackle onto a non-absorbent paper plate.
Mix one of your acrylic colors into the spackle. (Use a shade darker than your desired result because the white spackle will lighten the paint color.)
Mix thoroughly.
For decorative frosting, use 4 heaping spoonfuls of lightweight spackling and mix with your other acrylic paint colors.
Add each color frosting into piping bags.