I have a cotton print top with a white background whose colors have run in the cold wash cycle. How can I remove the unwanted color but still keep the garment’s pattern?
If the colored part is transfer-printed onto the white fabric (as in iron-on or heat transfer), then it would be very unusual for that color to bleed into the wash water and transfer onto the white part. Instead, the color would have come from another item in the wash load. If that’s the case (and as long as the white shirt doesn’t also contain any spandex, which should never be bleached), then you could try restoring the color with a bleach soaking solution. To do this, add 3 tablespoons Clorox® Regular Bleach2 to 1 gallon cool water and fully submerge the shirt for up to 5 minutes. Thoroughly rinse the shirt and then allow it to air dry.
If your shirt was made with a different process for applying the color, and it actually is responsible for the dye transfer, then you may want to try treating it with a very dilute solution of RIT color remover, which is available from drug and craft stores. The trick with RIT is to mix up a solution that is just strong enough to strip off the fugitive color, but not so strong that it also takes off the original color, so start by making up a very weak solution and see how it goes. RIT can also work well for removing color that bled from a colored section of an item into a white section but didn’t uniformly color the white part. If that’s the case, you have to be extra careful to get the shirt to air dry as quickly as possible so the colored sections don’t bleed all over again. Rolling the shirt in a towel to squeeze out as much excess moisture as possible will help. Hanging the shirt to dry in a warm room (or outside on a warm day) will also help.