That's what I'd try first. If you get a good match it's a tougher paint than nail polish. If you can't match it then fall back on the nail polish method.

Try a small dot on the bottom of the BB shell or somewhere else it's not visible. If it dries to near invisibility then it's a good color match be it proper paint or nail polish. Be super fussy on this. If it doesn't dissapear to your eye then it'll look like your frame has the measles when you fill in the top coat.

Anther option if the frame and company are still current is to emial or snail mail them asking for a touch up bottle. I know most new bikes and frames I've bought came with a little vial of touch up paint.