Here are some ways to remove red hair dye:

1. Use a clarifying shampoo to remove any built-up dye.
2. Use a baking soda and water mixture to help strip the dye from your hair. Mix 1/4 cup of baking soda with 1 cup of water, and apply it to your hair. Let it sit for 5-10 minutes, then rinse it out.
3. Use natural ingredients like lemon juice, vinegar, or vitamin C tablets. These mixtures are applied to the hair and left for 15-20 minutes before rinsing.
4. Use dish soap or color-removing products to strip the dye from the hair. These products contain chemicals that break down the oils and pigments in the hair.
5. Use a green-based ash hair dye to neutralize the red tone. This method requires choosing the right shade of green to match your hair color.