Mix icing sugar, water and meringue powder until blended. Spoon into separate bowls to match desired number of coloured frostings. Tint frosting in each bowl with desired food colourings. Spoon frosting from 1 bowl into piping bag fitted with small piping tip, such as a number 2, 3, or 4. Repeat with remaining frostings to fill additional piping bags fitted with small piping tips.