Medellín is 6 hours behind Stockholm
Best overlap: 2:00 PM to 6:00 PM in Stockholm is 8:00 AM to 12:00 PM in Medellín.
The overlap falls at 2:00 PM to 6:00 PM in Stockholm, or 8:00 AM to 12:00 PM if you're in Medellín. You've got a decent 4-hour window. Set a recurring time near 2:00 PM in Stockholm (8:00 AM in Medellín) and stick to it. Because only Stockholm changes its clocks, the overlap above isn't fixed; expect a one-hour shift when Stockholm enters or leaves daylight saving.