Removing color from towels to create white towels is possible, but only with certain kinds of towels. Many high-end towels use bleach and fade-resistant dyes meant to withstand heavy use. They are not supposed to be used with chlorine bleach, and their colors cannot be changed in an attractive manner. Colored towels without special finishes can have their colors faded or removed. It's impossible, however, to remove color from towels to create white towels without damaging the cloth fibers at least a little. Removing the color gently will create minimum damage, and removing it harshly will create maximum damage.
Slip on a pair of old clothes you don't mind accidently bleaching, an apron and some rubber gloves. Place the three, plastic, 6-qt, tubs outdoors on a flat surface. Fill the first tub with 15 cups of hot water and 3 cups of chlorine bleach. Fill the second tub with 15 cups of cold water. Fill the third tub as directed by the neutralizing product packaging.
Dampen up to four, clean, colored towels with warm water. Submerge the towels in the bleach-filled tub. Let the towels soak in the bleach for 15 to 20 minutes.
Wring the towels out, and place them in the tub with the cold water. Let the towels soak for 5 minutes, and wring them out well.
Place the towels in the neutralizer tub, and follow packaging instructions. Wring the towels out well.
Place the wet towels in a washing machine with a little laundry detergent. Wash the towels, and throw them in the dryer. Dry the towels.
Repeat the entire process as many times as needed to remove color from towels and turn them white.