Rather confusingly, there are several red taxis driving around Hong Kong dressed up as green taxis.

In Hong Kong we have red “urban taxis” that have higher fares and can operate everywhere except the south part of Lantau island.

Green taxis can only operate in the more northerly parts of the New Territories (such as Tai Po and Tuen Mun), and the east (Ma On Shan and Sai Kung, but excluding Tseung Kwan O).  Here's the map (pdf).

They can also go to a few special locations (e.g. Tsing Yi and Tseun Wan MTR stations, the airport, some hospitals, Disneyland, Sha Tin racecourse) and on some highways.  Details are here.

If you look closely when you are travelling around Hong Kong, you might notice the signs showing roads that are prohibited for green taxis.

Apparently there are only 75 blue Lantau taxis (operating on Lantau Island and Chek Lap Kok).

It’s an odd system.  If you live at the edge of the New Territories taxi zone and want to go out of that zone, you either have to wait for a red taxi, take a specific route (e.g. to Tseun Wan MTR), or negotiate with the driver of a green taxi to take you somewhere he’s not supposed to go.  Or take a minibus.     

So it’s rather strange that an advertiser is allowed to turn a red taxi into a green taxi.