Medellín is 6 hours behind Barcelona
Best overlap: 2:00 PM to 6:00 PM in Barcelona is 8:00 AM to 12:00 PM in Medellín.
For the smoothest call, aim inside 2:00 PM to 6:00 PM in Barcelona, i.e. 8:00 AM to 12:00 PM in Medellín. Since Medellín is 6 hours behind Barcelona, the workdays overlap by around 4 hours; 2:00 PM in Barcelona (8:00 AM in Medellín) makes a reliable recurring slot. Daylight saving complicates things slightly: Barcelona observes it, Medellín doesn't, so the difference flexes by an hour part of the year.