Disclaimer: The blue and green spirulina, and red algae pigments in this video were gifted to me as free samples by Spira Inc.
Ratio:
1/2 cup milk
1/4 cup vinegar
2 tsp baking soda
pigment of choice! doesn't have to be algae.
Traditionally you would use a borax in this recipe and heat the mix to speed up the reaction but I chose to use a more kid-friendly recipe in case anyone wants to do it with the family.