One 12oz. Beer - any beer will do although lighter colored beers will display the green better
Green food coloring - one drop
Add one drop of green food coloring to a clear glass. Pour the beer into the glass. That's it! This works for any beer. Darker beers like stout will have a nice green head atop their normally dark bodies. Serves 1.
Can also be done by the pitcherful.........adjust green food coloring accordingly!
Courtesy of: http://beer.about.com/od/drinksmadewithbeer/r/GreenBeerRecipe.htm