Natural color shades will look different depending on the type of icing. The variations in color are because artificial dye-free colors, made from natural plant-based sources, tend to react to the icing pH. As a rule, the higher the pH the darker the hue, and the lower or more acidic the icing, the brighter the shade.

When making a simple icing with powdered (confectioners) sugar and milk, the pH is neutral, and the colors will be closer to their expected hues. This icing doesn’t harden as quickly as royal icing and can have more of a glaze-like consistency. The icing itself might appear somewhat transparent but will saturate when adding natural water-based colors.

Generally, when working with natural coloring, royal icing has more color shifts than basic icing. Royal icing includes egg whites, which are naturally at a high alkaline pH. So, in royal icing, yellow from turmeric will shift to an orange hue, and pink from beets will turn magenta/purple. However, some royal icing recipes include lemon juice, which might neutralize the pH by adding acid, thus reducing color shifts.

The most pH sensitive natural colors are those from plant-based sources that contain a pigment called anthocyanin. Anthocyanins are found in fruits and vegetables like black carrot, purple potato, grape, and cabbage. Anthocyanin colors will turn redder with acid or purple with alkalinity. Similarly, flowers such as hydrangeas which also contain anthocyanins, change color due to the acidity of the soil.

Spirulina, sourced from algae is less subject to color shifts with pH fluctuations. This is also true for carotenoid colors, such as carrots, oranges, tomatoes, or saffron.

Some natural color products might already contain citric acid or sodium bicarbonate (baking soda) to adjust or maintain the color. It’s good to be aware of any incidental ingredients in the colors before working with a recipe that has a high or low pH that might affect color change.