Hi dilligaf,
Our silver casing looked quite black, before I decided to try and remove it using something more than a damp cloth!
Used some soapy water ('fairies') (making sure of course the cloth was well rung out) and hey presto it worked. Although we have a new TV now, have just tried maviscoull's suggestion on the old one - and yes the baby wipe was quite black when I had finished cleaning!
Incidentally I only purchased the wipes on recommedation that they were excellent for removing paint (water based) from your hands when decorating!!
The advert should read "Not just for baby's (babies) bums!!" lol