Here's what you can do:
1) If the scratch is not deep, try using polishing compound to buff the scratch out.
2) If the polishing compound works a little, try rubbing compound but take it easy.
3) If no paste-abrasives can fix it, it's time for paint. You can buy Dupli-Color paint pens for 3$. They work GREAT. Just match your color code with one on the pen and it will look perfect. Run a small streak of paint from the pen onto the scratch. Even it out as much as possible with the pen. Then, use 1500 grit sandpaper on a pencil eraser to lightly lightly buff the paint thin. I recommend taping the surrounding areas so the sanded materials don't work themselves into the paint.
Let it dry again and make SURE to wax over it- especially if you tried the rubbing compound.
If that doesn't work, then it's time to sand the paint down a bit and paint it with a sprayer. I tried it a few times and it's not HARD, but I recommend trying it on scrap sheet metal first.
But, the Dupli-color pen should work fine. I had a gash on my door from the time I bought the car. The pen fixed it- you can barely see the edges from a foot away. Just make sure to use a 1500-2000 grit sandpaper edge to buff the streak down or it will look lumpy close up.
4) Find the A-hole who scratched your car. When you know their name and address, go to a local farm and ask if people can buy manure from them. If yes, request that a tanker full of chicken poo get dumped on the A-hole's front lawn at 2:00AM (because he works 2nd shift).
I had to.
Scratch on my 2005 coupe passenger door 
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