In a bowl, mix together a spoonful or two caramel sauce (the thicker the better) and a few drops of red food coloring. Rim a martini glass by dipping it into the caramel and then turning it, so the sauce drips onto the glass, not away from it.
Combine all cocktail ingredients except soda water in a shaker with ice. Add just 1-2 drops of blue food coloring to brighten the green color, not so much it turns blue. Shake well to combine and then strain into martini glass. Top off with soda water.