touching up scratched paint on plastic

[GobotFool]

Hey all, I have a small paint scratch on the chest of my metal material gundam. While not very large, because it's white plastic under royal blue, it stands out like a sore thumb. Any tips on how to touch this up? Any one have any idea what type of paint to use? I was thinking maybe the Blue Gundam marker would do the trick but I don't know how fine the tips are on those things.