You can use Head & Shoulders shampoo to strip the colour from your hair. When you wash your hair with it, leave it on for 20-30 minutes, and then once you rinse it out, soak your hair in conditioner because this shampoo can dry your hair out. This method is quite inexpensive and will quickly take the dyed colour out.
If you cannot find Head & Shoulders, a clarifying shampoo will often do the trick as well.
If you cannot find Head & Shoulders, a clarifying shampoo will often do the trick as well.