From what I understand, Heinz carries a line of colored ketchups, one being called Funky Purple and one called Blastin' Green, which are a big hit with kids. Well, this is a fun Halloweeny recipe to get the kids involved...edible wormy hot dogs on a bun topped with purple ketchup. As the recipe specifies, if you can't find the Funky Purple ketchup, make your own with a few drops of blue food coloring.