Start by making the tapioca pearls, in a small bowl mix the boiling water and food colouring. Add the starch and mix until the dough starts to come together.
Turn onto a flat surface and knead until smooth. Roll dough into a 2cm width cylinder. Cut into even small pieces, approximately ½cm wide. Roll into balls. Bring a pot out of water to the boil then drop in the pearls, stirring to separate. Boil for 15 minutes then drain and transfer to a bowl, cover with room temperature water.
Meanwhile, to make the tea. Bring a pot of water to the boil. Stir in the baking soda and taro. Boil for 10 minutes then drain. Allow to cool completely then combine condensed milk, milk and taro in a blender and pulse until well combined. Divide pearls among serving glasses and pour over equal amounts of tea and top off with ice.