According to FurnitureClinic, faint scratches on a leather couch may be hidden using leather recoloring balm. Deeper scratches require more extensive trimming, sanding, and coloring in order to hide.
First, clean the dirt and grime from the scratched area using Leather Ultra Clean. Use sharp scissors to trim any long, loose fibers from the affected area. Shorter fibers can be left in place as they will not affect later stages of repairing the scratch. Next, apply leather binder with a sponge to the damaged area . Apply eight to ten coats, and give each coat enough time to dry before applying the next one. After applying the binder, sand the area down with 1200 grit sandpaper until the surface is smooth and even. Make sure the area has no residue from the sandpapering. Then spread a thin level of heavy filler using a palette knife. Let the filler sit for 20 to 25 minutes, and apply extra layers only as needed. Afterwards, sand the area once again and wipe the area down with alcohol cleaner. After the leather dries, apply the first layer of colorant with a sponge. Build as many thin layers of colorant as needed to blend in with the area. Finally, use a sponge or airbrush to apply three to four layers of Super Seal, and apply four to five layers of Leather Finish.