Cover the affected area with some heavy-duty liquid detergent.
Add a little bit of hot water over the detergent, and allow the stain to soak for three minutes.
Soak up as much of the excess moisture as you can using a dry rag. Blot the stain instead of rubbing it to avoid making the stain worse.
Add some rubbing alcohol over what remains of the stain, and allow it to fully penetrate for another three minutes.
Blot the rubbing alcohol out of the couch using a clean towel. Allow it to air-dry.