The technical term for removing colour from fabric is discharge dyeing. In order to discharge colour, you must use bleach. Bleach should only be used on cotton, linen or other natural fibres. Bleach should not be used on wool, silk or polyester. In order to remove colour from fabric, you can use common consumer bleach that can be found at local grocery stores. Bleach is a highly toxic chemical and should only be used in a well-ventilated area.
Prepare your work space in a well-ventilated area. Cover the surface with a large bin bag. Set aside two buckets; one for diluted bleach and another for water. Put on rubber gloves to protect your skin.
Combine bleach and water. The bleach will need to be diluted to avoid ruining the fabric. To dilute bleach, pour 1 part bleach to 4 parts water into the waiting bucket. Fill the other bucket with water.
Place the garment in the bucket of bleach and water solution. The garment should be left in the bleach solution until all the colour fades out and it becomes white. If the diluted bleach solution does not produce the desired effect, add more bleach.
Remove the garment from the bleach solution. The garment should immediately be rinsed in the bucket of water.
Take the garment out of the water bucket. Place it in the washing machine and wash it in cold water. Dry the garment per fabric instructions.
Contrary to popular belief, there is technically no such thing as white dye. Some colours and fabrics can be whitened with bleach. Keep in mind that bleach is a powerful chemical and can cause the deterioration of fabric. Some fabric shops carry colour dischargers. They may not be as effective as bleach, but they're less harmful to the fabric.