Colombo is 13.5 hours ahead of Portland
There is no standard 8-to-6 overlap. Someone joins early or late.
Set against a 13.5-hour difference, Portland and Colombo run their workdays on completely separate schedules. Block a single recurring off-hours slot that both teams agree on, rather than negotiating a new awkward time every week. Note that Portland follows daylight saving while Colombo stays put, so the times above drift by an hour seasonally.