Add the arrowroot powder, baking soda, colorants, and essential oils to a food processor or blender. Blend until the mixture reaches a fine powder consistency.
Add the dry shampoo to a refillable makeup brush or powder sifter.
To use, dispense a little powder and apply it to the roots of your hair.
Let sit for a minute or two, then use your fingertips to distribute the mixture throughout your hair evenly.