Ingredients such as added flavors, vitamins, and polyphenols can interact with different natural colors. Vitamin C, for example, enhances the stability of natural beta-carotene, but weakens the color stability of anthocyanins.
Blue, green, and purple hues are more difficult to achieve for ready-to-drink (RTD) beverages because spirulina extract is not currently approved for use in RTD beverage applications in the U.S. per FDA CFR Title 21 and it is not stable to heat or light. However, it is well suited for powdered drink mixes. Because there is such a wide variety of beverage types and available natural colors, it is often necessary to work directly with color experts to create custom blends to achieve the right hue that will function properly within a particular beverage system.