In the mixing bowl of a stand mixer, place the warm water, meringue powder, and Karo syrup, and blend with the whisk attachment until completely blended and smooth.
Add the powdered sugar, about 2 cups at a time, and mix on low, until all the powdered sugar has been added. Scrape down the sides of the mixing bowl as needed, and blend until the Icing is smooth and creamy.
In four bowls, evenly place about 1/4 of the icing in each bowl. In one of the bowls, add 2 teaspoons of Watermelon Flavored Jello, and 2 drops of Hot Pink Food Coloring Gel. In another bowl, add several drops of Lime Green Food Coloring Gel. In the next bowl, add a few drops of the Dark Green Food Coloring Gel, and in the last bowl, add a few drops of the Black Food Coloring Gel.
Place the icing in 4 plastic pastry bags, and snip off the very end of the bags.
Pipe the Lime Green Frosting in two lines, on the rounded side of the cookie, one on the outside, and one right at the pink color, leaving just enough room to pipe a thin strip of the Dark Green Icing between the Lime Green piping.
Fill in the cookies with the watermelon colored icing.
Pipe small dots of the Black Icing all around the rounded side of the cookie, and using a cookie scribe pull the black icing down on the body of the cookie, which will resemble Watermelon Seeds.
Allow about 1 hour for icing to completely set.