Fresh henna powder smells like fresh cut spinach and is an earthy green or khaki color. Bright green powder may have chemical dye added; this is often just a food coloring and can be safe. If the powder is brown and has little or no scent, it may be stale and too old to yield a good color for Mehndi or henna body painting.
Henna powder is light and heat sensitive as it is an organic product with no preservatives added. Store henna powder sealed tightly and protected from light, air, and moisture in the freezer.