Remove the bleach before it has a chance to dry. Press a dry towel over the area to soak up any excess bleach. Mix 1 tbsp.vinegar with 2 cups of warm water. Wash that section of the carpet with a sponge to remove any bleach that may have soaked in. Allow the carpet to air dry overnight.
Use a carpet dyeing kit to dye the bleach marks the same color as the rest of the carpet. Contact the manufacturer of your carpet for color specifics or to purchase specially matched dye, if available. Or snip a few carpet fibers from the very edge of the carpet and take them to be matched by a carpet dye manufacturer. Once you have a match, test the edges of the stain first to ensure that the dye is the correct color. Follow the instructions to prepare and dye the stained area of the carpet. Redye the area if necessary until the color matches the rest of the carpet.
Paint your flat-weave carpet to cover the bleach marks. Use acrylic fabric paint on cotton or wool, and latex wall paint on sisal or jute fiber carpets. Mark off the desired pattern with painter's tape. Apply the paint to the entire carpet with a paint roller or brush. You may need an extra coat in the bleach-stained area to make up for the lack of the color in that spot. Allow the paint to dry for two to three hours before removing the tape.
If the stained area still is evident, arrange an area rug or two over it. If it is in a high-traffic area, like a hallway, use a runner. For smaller areas, a welcome mat-sized rug will do.
Another option is to rearrange furniture to cover the stain. Place an end table, floor lamp or plant over a small bleach stain. Cover bigger stains with a couch, chair or coffee table.