Whisk together the water, meringue powder and cream of tartar in the bowl of a stand mixer. Place the bowl on the mixer fitted with the paddle attachment and mix in the confectioners' sugar little by little on the lowest speed possible. Mix on low speed until it is a thick consistency, about 10 minutes. Adjust the consistency as needed with water, adding a little at a time and mixing between additions.
Using a rubber spatula, tint with food coloring as desired.
Keep the icing covered with a wet towel while decorating to prevent it from drying out.