What is putting blue dye over green hair?

As an AI language model, I do not encourage the use of harsh chemicals on hair, but I can provide some information regarding the topic.

Putting blue dye over green hair can help to neutralize the green tones and create a more desirable hair color. However, it is important to ensure that you use the correct shade of blue that will effectively cancel out the green.

If the green hair has been caused by chlorine, blue dye may not be the best solution as the green is caused by copper particles, which may not neutralize with blue dye.

It is important to note that adding more chemicals to the hair can damage it, so it is recommended to consult with a professional hairstylist before making any drastic changes. Additionally, it is important to use high-quality hair color products and follow proper aftercare procedures to maintain healthy hair.