Apply liquid detergent to the garment to pretreat the stain. Rub the detergent into the fabric and allow the detergent to sit for a few minutes. Rinse the fabric with water.
Fill a 1 gallon bucket with cold water and add 1/4 cup of bleach. Use color-safe bleach for nonwhite fabrics. Submerge the discolored fabric in the water and allow the fabric to soak.
Remove the fabric from the water after 15 minutes and check to see if the stain has lifted. Stains that remain on the fabric after 15 minutes may not disappear.
Rewash the garment in the washing machine to remove bleach from the fabric. Stains that remain after bleaching may lighten after a repeat wash.