Colombia visa exemption for US Green Card holders may not apply at the border if you have an I-797 extension.

TL;DR: If you are traveling on an expired Green Card with an I-797 extension letter, be aware that while this is valid for US re-entry, it may not be recognized by foreign border authorities. We were denied entry to Colombia, separated, and spent 24+ hours in transit limbo.

I have a US passport and my husband holds an Indian passport and a US Green Card. His physical card had expired, but USCIS had issued a standard I-797 extension. It's legally a valid proof of Permanent Resident status in the US. Colombia's official policy grants visa-free entry to nationals of 8 countries (India, China, Cambodia, Myanmar, Nicaragua, Thailand, Taiwan, Vietnam) who hold a valid US permanent residence permit.

Official sources:

• Colombian Cancillería entry policy — lists the 8 nationalities and the permanent residence permit exemption.
• Indian Embassy Bogotá travel advisory — confirms Indian travelers with a US residence permit don't need a visa

We thought we were covered. We were not.

Upon arrival, the Colombian immigration officers refused to process the I-797 extension paper. They claimed that because it wasn't a physical, unexpired card, it was not "valid proof" for them. Despite our attempts to show official documentation and use translation tools (they did not speak English), they refused to engage. Things escalated quickly. They separated us immediately, confiscated his passport/documents, and placed him in a secure detention holding area. I was forced to clear customs and leave the area while he was detained.

What actually happens when entry is denied, because no one tells you this.

• The denied passenger is escorted by immigration agents to a holding area. They will be physically separated from their traveling companions. Their passport will be taken, and from then on the passport will move hands between airline crew members and immigration officers until you land in the US.
• The airline that brought you is responsible for returning you to your origin city. That's not optional and they cannot rebook you anywhere else. If you are separated, try to get a contact person at the airline immediately. Stay calm, but be the squeaky wheel and urge them to get you back home on the next earliest flight.
• Any transit country treats the denied passenger as inadmissible. You won't be able to leave the transit airport either (if you book a long layover flight or a separate one out) even with fully valid US documents.
• Being separated in a foreign airport without clear information is terrifying. If this happens, your primary goal is to get back to US soil. Don't waste energy trying to fight the decision once the officer has made it; focus entirely on the logistics of the return flight.
• We finally cleared US immigration without any issues, but the uncertainty during the flight was the most stressful part. We are just grateful to be home.

So the I-797 is not accepted, do I apply for a Colombian tourist visa then?

The official system tells you that you don't need a visa. The border tells you your documents aren't valid. Example: TripAdvisor post. There is no clean path written down anywhere. If you are certain you want to travel to Colombia, then contact the consulate to get the visa before your trip. Make sure you document the exchange if they push back saying you don't need one.

Also, do not rely on airline check-in approval. Copa airlines staff verified our documents in San Francisco and let us board our flight to Colombia. Colombian immigration was entirely separate.

Useful search tip

Most people search with a combination of "Indian passport + US Green card, do I need a tourist visa for Colombia?" and get the visa-free policy. It won't surface this edge case. Search specifically: "Indian passport with US green card and an I-797 extension. Do I need a tourist visa for [Country]". Do this for every country you plan to visit. I checked and found Mexico has a similar experience. Haven't checked others.

We're home now. But I hope this saves someone else the trip.