After my hair was pink and teal I covered it with some brown dye on the pink & black dye on the teal (because the teal would NOT come out and nothing would cover it except black). I didn't want all black hair, so I decided to just two tone it, but for my wedding I knew I wanted one color, so I went back to the salon because I didn't have the knowledge or skills to remove the black dye and was worried I might destroy my hair trying on my own (not something you want to do right before your wedding). It took two appointments, the last being about two weeks from my wedding day and on that day he was going to bring it back to a natural redhead red, but instead I ended up with a red that was way more red-orange and intense than I had wanted. That night I stripped most of the dye he had put on with ION color remover and bought some dye at Target that was the color I actually wanted. Bam! Fixed. It was the exact color I wanted after I redyed it, haha! Oh well.
Keep in mind that I'm no hairdresser or colorist by any stretch of the imagination, so if you're not confident when DIYing your hair color I wouldn't advise doing it. Plus, any of the methods I used above are purely based on me going, "hm, I bet this might work!" so it's not really "expert advice" per se. My hair is pretty beastly when it comes to handling processing and being dyed, so I felt comfortable DIYing my color. Despite my hair being one of my most noticeable features, I don't mind playing around with it, it's just hair, after all! I absolutely adored being a redhead and would totally consider going back to it some day.