Unless you can get the EXACT paint the manufacturer used, I suggest not bothering with colored touch-up paint and going the clear nail polish route. (I once bought a frameset and the manufacturer supplied a small bottle of touch-up paint along with it, which was thoughtful.)

In my experience, even when the color is pretty darn close at time of application, differences can appear later as the touch-up paint reacts differently to sunlight, sweat, pollution, etc. (I am speaking from experience.) You might have better luck if your frame was painted to begin with (and you can lay your hands on it), but if the frame was powdercoated originally and you're like attempting to patch it up with paint, you'll likely be disappointed.

And black...well, let's just say that Testors' Gloss Black proved to be much grayer than my fork's gloss black paint (that time, the fork was actually painted), so now I have ugly gloss grey-black patches on my gloss black fork.

Mike