Remove as much of the stain as you can by dabbing the stain with a dry white paper towel or scrape it off using a dull knife.
Neutralize the stain with a 1 tablespoon of clear household ammonia to 1/2 cup of water mix. Saturate the spot with the mix using a spray bottle. Be sure not to wet the backing of the carpet. Blot with a white paper towel to remove excess moisture.
If the stain is still persistent, mix 1/4 teaspoon of a clear hand or dish washing detergent (which does not contain bleach or lanolin) with 1 quart of water. Use a dabbing motion to work the detergent into the stain. If spot is being removed continue applying detergent solution and blotting with a white paper towel until spot is removed.
Using a spray bottle, rinse with water and blot the area to remove excess moisture.
Spray lightly with water, do not blot this time; apply pad of paper towels and brick and allow to dry.
If some part of the stain is remaining on the carpet and blotting is not removing it, then moisten the fiber in the stained area with 3% hydrogen peroxide. Let it sit on it for an hour. Blot and repeat until carpet is stain free. Light will cause peroxide to change back to water so no rinsing is necessary.
Apply pad of paper towels and weight down with a heavy object.