Medellín is 2 hours behind Rio de Janeiro
Best overlap: 10:00 AM to 6:00 PM in Rio de Janeiro is 8:00 AM to 4:00 PM in Medellín.
Target 10:00 AM to 6:00 PM in Rio de Janeiro, which lands at 8:00 AM to 4:00 PM for the Medellín side. That's a roomy 8 hours of common time each day, so finding a slot that suits everyone is rarely a problem.