The red sock in the white wash that turns white blouses and white shirts pink is a cliché, but that doesn't stop it happening. Somehow that red sock - or some other colored piece of clothing - finds its way into the white basket and then on into the white wash. The color runs, and your whites are ruined, right?
Well, no actually. In fact, if you take immediate action you should be able to get your whites back to normal with a minimal amount of fuss. It has to be stressed again that the sooner you can get to work on fixing this problem the better. Absolutely do not tumble dry your errantly-colored clothing - ideally you shouldn't let them dry at all. You will see that there is a problem as soon as you take the wash out of the machine, so that is when you will need to take action. It will probably mean a bit more time at the laundromat, but at least your wardrobe will not end up full of oddly pink-colored clothes.
The first step in getting your clothes back to white is to find the offending piece of clothing and remove it from the batch of clothes. Once you have that item removed, go through the whites and separate out any items that have not been affected by the color bleed.
Now put the affected clothes back into the washing machine. Use cold water only and add your detergent as normal. You should also add one cup of bleach to the wash. Because you are washing whites you can use chlorine bleach. If your problem is color-bleed on non-white clothing, make sure you use non-chlorine bleach.
There should be enough water in the machine to fully cover the clothes. When you are ready, put the machine on its highest agitation setting. By putting the clothes back into the wash straight away before the dye has had time to settle, and by agitating the clothes with cold water, detergent, and bleach, you will find the unwanted colors will be removed from your whites.
What If They Are Still Not White?
Sometimes you will get stubborn dyes that are not so easy to remove. If this happens you will still see traces of the color after going through the above steps. In this situation you should simply repeat the process: start a new wash and add bleach and detergent again.
If that still doesn't work you will have to let the clothes soak in a solution that contains bleach and water. The water should be cold, and you should let the clothes soak overnight. In the morning, go back to the laundromat and wash the clothes again using the recommended amount of detergent.
Once the wash has finished its full cycle, check the clothes carefully. Even if the stain remains after the first run through this process, you should nevertheless see it starting to fade. You simply have to continuing repeating the above steps until your clothes are back to white.