Medellín is 8 hours behind Riyadh
Best overlap: 4:00 PM to 6:00 PM in Riyadh is 8:00 AM to 10:00 AM in Medellín.
For the smoothest call, aim inside 4:00 PM to 6:00 PM in Riyadh, i.e. 8:00 AM to 10:00 AM in Medellín. The overlap barely stretches to 2 hours, so reserve it for what really needs a live conversation and handle the rest async.