Why did your freshly grated horseradish turn green?

Freshly grated horseradish can turn green due to the oxidation process that occurs when its enzymes are exposed to air. This reaction can produce chlorophyll and other pigments, resulting in a greenish tint. Additionally, if the horseradish was grown in soil rich in certain minerals, it might contain pigments that contribute to the color change. Despite the color, the flavor and pungency of the horseradish remain intact.