These striped and marbled designs are made by piping a second color of royal icing on the wet flood.
To create a striped and marbled designs with royal icing, start by piping and flooding with the main color.
While the icing on the cookie is still wet, pipe lines with a second color of icing on top, using the flood consistency icing. Use a piping tip (Ateco #1 or #2) to create finer lines. Stop at this point for a striped design.
To create a marbled effect, drag a toothpick through the stripes while the icing is still wet.