Place meringue powder, water, and powdered sugar in stand mixer fitted with whisk attachment. Mix for 7 minutes until soft peaks form.
Separate royal icing into three bowls. Do not dye one bowl of icing. Cover and set it aside.
Add red food coloring to another bowl of icing. Stir. Repeat, saturating with dye until it no longer changes color. Cover and set aside for two hours.
Meanwhile, add black food coloring to another bowl of icing. Stir. Repeat, saturating with dye until it no longer changes color. Cover and set aside for two hours.
Fit piping bags with couplers and a round #1 or #2 tip. Fill with royal icing and close with bag ties.
Baking and Decorating 8-Bit Cookies
Make sugar cookie dough and roll to 1/4" thick.
Cut out cookie shapes using 8-bit cookie cutter. Repeat until all dough has been used.
Bake cookies until edges are light golden brown. Let cool completely.
Pipe outline around edge of heart-shaped cookie using black royal icing. Let dry.
Pipe red royal icing just inside black outline. Let dry.
Fill inside of cookie with red royal icing. Let dry.
Pipe character name on cookie with white icing. Let dry.
For these heart-shaped Valentine cookies, I used a royal icing consistency that's between flood and piping consistency.
To make jet black royal icing, completely saturate the icing with black food coloring, then wait. At first, the black icing was dark green, but over a few hours, it turned jet black. The red turned from mauve to heart red.