Colombo is 5.5 hours ahead of Reykjavik
Best overlap: 8:30 AM to 12:30 PM in Reykjavik is 2:00 PM to 6:00 PM in Colombo.
For a call that suits both sides, look at 8:30 AM to 12:30 PM in Reykjavik / 2:00 PM to 6:00 PM in Colombo. With 4 hours of overlap, 8:30 AM in Reykjavik (2:00 PM in Colombo) is a comfortable, repeatable slot for both sides.