Hi,
You've cut through the black anodizing.. a process to keep aluminum from oxidizing. You may be hard pressed to make a perfect match.. but black fingernail polish might be easiest.. unless you have a LOT of scratches. Most people will not notice if your fix is slightly off. If it's black.. you may still see the flaw.. but only because you are looking for it. The alternate fixes get much more involved.. new aluminum trim, or trim to cover the old.
Best Wishes, HandyguyJ