What is blue hair dye over green?

If you apply blue hair dye over green hair, the result can vary depending on the shade and tone of the green hair and the shade of blue hair dye. If the green hair is a yellow-based green, it can mix with the blue and turn into a turquoise color. If the green hair is a blue-based green, it can mix with the blue and turn into a darker green. To get the best results, it is recommended to remove any existing hair color or to lighten the green hair using a bleach wash before applying blue hair dye over it.