In 1892, 14 British pillar boxes were installed in Hong Kong and until the handover to China in 1997 thousands more serviced the territory. What is left are painted green and it was reported in October 2015 that Hongkong Post planned to put a plate over the remaining 59 post boxes with royal insignia that are still in service to 'avoid confusion'.
There haven't been any riots over post boxes yet but it's not a bad idea to visit some of them before they are gone. Two are very difficult to reach - one is in the closed frontier area with China and one is in a mental hospital.
There are 73 British era post boxes left in Hong Kong, 64 in service and 9 on display:
You can find them all on the Hidden Hong Kong Map