Both offices are open 09:00–15:30 Colombo time — 6.5 hours together.
09:00 you → 11:30 Singapore
10:00 you → 12:30 Singapore
11:00 you → 13:30 Singapore
09:00→11:30Singapore is at work
10:00→12:30Singapore is at work
11:00→13:30Singapore is at work
12:00→14:30Singapore is at work
13:00→15:30Singapore is at work
14:00→16:30Singapore is at work
15:00→17:30Singapore is at work
16:00→18:30outside Singapore working hours
17:00→19:30outside Singapore working hours
Working hours assumed 09:00–18:00 local. Offsets include daylight saving where it applies, so this shifts through the year.