Adrian, Brasso and toothpaste are both mild abrasives. (Brasso has all sorts of other nasties in it too - you'd probably never get the smell of it off your MBP screen - methinks it's petroleum based and it's nasty smelling. I don't even like polishing brass with it and use other products)
At any rate - a mild abrasive is likely to do MORE damage to your screen (especially if it's a glossy one) and will do nothing to remove the gouge.
You might want to give us a bit more detail on "starting to get some different coloured whites and stuff like that" - when does this happen and what exactly is happening? Color problems can have different causes and not all of them are the fault of the display itself.