So you have a really bad hair color. What do you do? Do you panic? Do you cry and shake your fist at the sky, cursing the hair gods? No, the first thing you must do is logically take stock of your situation. Did you do this horrid deed to yourself, or did a professional do it to you?
If it was a professional, contact them immediately to tell them that there is a problem with your color. You have 48-72 hours before it becomes a completely locked-on, permanent color, so you will need to hurry and get your correction appointment booked as soon as possible. And do not throw a hissy-fit over the situation. It's not attractive and it's not going to make anything better. Focus on what's important, and what's important is getting the problem resolved.
If you did this to yourself, first turn to a professional color correction expert. If you can't do that, call the number on the box in which your dye came or the brochure inside. Have the box available to answer any questions they may have for you at this phone number. It's best to avoid doing anything on your own to try to correct your dye job, as it can make your hair even more difficult to fix.
And then there's always the ride-it-out option, in which you remain as positive as possible and try to live with what you couldn't get undone. For example, you could take hot baths or showers, which are well-known for fading hair color. You could also use a color shampoo in a shade that you like. There's also the bonus for those of you with green hair, that you could get a red color shampoo and it may help to neutralize your hair color a bit. You can wear hats until your color grows out, or you can embrace it and pretend that purple hair was exactly what you were aiming for. After all, we live in a time when you can have a pretty free choice of hair colors in almost any job you work, with the right attitude.