i dunno exactly how it works but a similar thing happened to our tv a while back.

a guy in the electronics store said if you take the back panel off, there's a certain section where some small screws can be turned with a flat head screw driver.

turning these affects the colour, brightness and sharpness and with a little tinkering my dad managed to get the proper colours back plus sharpen the picture up big time.

the only downside was that we were set to get a widescreen plasma but my mum heard the shop guy telling my dad how it could be fixed