What’s the Cantonese word for rainbow? Choi Hung, of course!
Most of the original MTR stations (not counting the KCR lines) were tiled in a particular colour. Each station was tiled up in a given colour or two. The stations name would be mounted on the wall (so you knew where you were, of course) or pillar on the tube floor. These gave a distinct flavour to the Hong Kong MTR stations that the sterile metros of Kuala Lumpur and Singapore did not.
Unfortunately a lot of MTR stations are being converted to plastic / acrylic wall coverings, slowly removing the local flavour. A pity really. In certain stations, you can see some sections are still tiled but others have been covered up with shiny plastic facades.
Choi Hung station is special in that its signage pillars (pictured above) are not done up in a single colour but like its namesake, is done up in a rainbow of colours.
So at rainbow station, the station signage is rainbow-coloured. Very nicely done.