Try Magic Eraser for superficial scratches!
I was looking through this forum, hoping for a fix for slew of scratches on my 2-week old Macbook Air. I also tried various cleaners with no luck - but I happened to also try a Magic Eraser and they are gone!
Now these weren't gouges in the surface of the unibody but metal to metal scratches from a pen clip in my briefcase rubbing against it on a 5 hour flight from LA.
Anyway - give the Mr Clean Magic Eraser a try, it can certainly removed those small discolored scratches.