Place the confectioner's sugar in the bowl of a tabletop mixer fitted with the flat beater. With the mixer running on medium-low speed, add the almond paste about 1 teaspoon at a time. This will take about 5 minutes.
Once you have added all of the almond paste, the mixture will be crumbly. Scrape down the bowl and beater.
Add the corn syrup and mix on low speed until incorporated. The mixture will still be crumbly. Again scrape down the bowl and beater.
In a small bowl, combine the water and the food coloring. With the mixer on medium-low speed, add about half of the food coloring mixture and beat until incorporated.
Continue gradually adding the food coloring mixture until the marzipan just comes together and reaches the consistency of sugar cookie dough. It should be smooth and not crumbly or overly sticky.
If more color is desired, knead it in by hand after removing the marzipan from the mixer. Remember it is easier to add a little more color at the end than to make a new batch. Different colors have different intensities and will require different amounts.
Place the marzipan on a sheet of plastic wrap and form it into a 9-inch round disk about 1/2-inch thick. Wrap and refrigerate overnight before using.
The marzipan may be stored in an airtight container or covered in plastic wrap in the refrigerator for up to 1 month.