Removing blue hair dye can be a tricky process that requires care and caution to be executed properly. There are different ways to attempt this depending on if the blue dye is permanent or temporary hair color. Oftentimes, the only way to get rid of dramatic colors is to bleach the hair or dye over it; however, with help from a salon or multiple shampoos if the color is temporary, there may be other ways to get the blue dye out of your hair.
Create a mixture of baking soda and shampoo. Choose a clarifying shampoo. It does not matter what the brand is, but the label should say "clarifying". The mixture should be one part baking soda for every two parts shampoo. For example, if you use a tablespoon of baking soda, mix it in with two tablespoons of clarifying shampoo. You can lather and rinse as many times as desired, however, this is a process that really tends to damage the hair and strip it of moisture, so take caution.
Use dish soap on your hair. It does not need to be mixed with anything, although it is possible to mix two parts dish soap with one part powder laundry detergent. Lather and rinse as many times as necessary, keeping in mind the potential damage being done to your hair.
Make a mixture of crushed vitamin C tablets and shampoo. Once again, the mixture should be one part vitamin C tablets and two parts shampoo. Lather and leave in for 10 minutes.Survey your hair and repeat if necessary.
Dye over your hair if possible. While this is not always recommended, if your blue hair dye is only semi-permanent and you have dark hair, dyeing over it with permanent color may be a solution. This is trickier with lighter hair colors; if you have blond hair, dying over blue hair with blond is not recommended. The blue will either show through the blond dye or mix with it, leaving you with green hair.
Bleach your hair. While this is an extreme option that should be considered a last resort, it will definitely get the blue color out of your hair -- as well as all the rest of the color, too. Use a volume-30 developer with blond powder bleach and mix them together in a bowl, depending on the instructions on the blond powder bleach kit. Section off your hair and leave the bleach in for 30-45 minutes and rinse it off. You are now free to add your own color to your hair.
Go to the salon. This is the best way to start going about the process of getting the blue out of your hair, because the professionals at the salon can give you advice depending on your particular situation. They will likely either color over your hair, bleach it or give you your own steps to follow. Whatever the case, going to the salon about your blue hair is a smart step and a safe bet.