Upvote:5
According to the US Department of State, yes, you will need both your US passport and your Colombian passport to make this trip:
All Colombian citizens—regardless of dual citizenship—MUST present a valid, non-expired Colombian passport to enter and exit Colombia. Colombian citizens traveling with non-Colombian passports may be unable to depart the country until they obtain a Colombian passport.
Be aware that any person born in Colombia or of Colombian parentage may be considered a Colombian citizen, even if never documented as such.
Be aware as well that all U.S. citizens, regardless of dual citizenship, must present a valid U.S. passport upon returning to the United States. Persons who are both U.S. and Colombian citizens MUST travel between these countries with both passports, presenting the Colombian passport upon departing Colombia and the U.S. passport upon arrival in the United States.
US consular information like this is generally written reactively after other people in similar situations have had a problem, (as has, for example, this previous Stack Exchange questioner) so I would take the warning seriously in your situation — it sounds like you do not want to get stuck in Colombia waiting for a new passport if you can avoid it. Get the paperwork done beforehand, so you can enjoy your trip!