[filcord]

I agree with Sam. Modern cars have a clear coat over the actual pigment. If the pigment layer is a metallic paint, this makes it even more difficult to touch up. I have an automotive paint shop, and my employees can match any shade with 100 per cent accuracy, but this will still require a professional to apply. Maximum you can do is to purchase about 50 ml of the exact coulour of your car and touch up a tiny scratch with a fine artist brush, but this is only to prevent the spot from getting rusty. If it's a major scratch, go to a professional.