If the black is stable mild PH prespray and acid side rinse, extra vacuum passes and maybe even leave an airmover if they don't live too far out. If too far, extra vacuum passes and terry towel to get any extra moisture, clean steps first leave airmover on it while you're cleaning the carpet to allow to dry as much as possible.
If you pull any color I'd use a dye stabilizer and neutral cleaner and acid rinse, leave airmover overnight and charge a premium....more than your usual.