A natural blue colorant solution comprising red cabbage liquid, aluminum sulfate and sodium bicarbonate is disclosed. The pH of the colorant solution is in the range of 3.8 to 4.2 and can be used to provide a blue hue when incorporated into products having a pH greater than 5.5. A highly stable blue colorant solution is created when the weight ratio of the aluminum sulfate and sodium bicarbonate is approximately 2:1. The blue colorant solution can be modified to create a natural green colorant solution by the addition of a natural yellow colorant and additional sodium bicarbonate.