Sometimes when you buy new clothes and towels that are dark coloured, the dyes from the fabric will run in the wash and stain other items. Making the items colour-fast will ensure that the fabric won't stain or ruin other items in the washing machine. When a red shirt dyes a sock pink, that is what happens when clothes are not colour-fast. Anything can be made colour-fast, and you won't have to worry about your clothes getting ruined.
Prepare your colorfasting solution. Fill a bucket with a gallon of cold water, and add 2/3 cup of vinegar to the water.
Place your item inside the vinegar and water mixture and let it get completely wet. The fabric will need to soak for an hour.
Remove the item from the vinegar soak and toss it into the washing machine with like colours. Launder the item as you normally would.
If you are colorfasting a lot if items, group them into like colours to do batches. Otherwise, items of different colours will need to be put into the vinegar solution separately. You may need to rinse out your bucket and prepare a new solution if dye comes out into the water.