Matching the original paint close enough to have the result not look like a bike with the measles is quite difficult, IME. I usually leave the paint alone. A bike should look its age.

The only time I've done a partial paint job was when I had a matching fork in the wrong color. I had had paint matched and mixed at a local DIY store, repainted the fork by hand with a brush to make sure the finish didn't look too new, and re-lined the lugs to blend it in. I didn't dare touch the spots and scratches on the frame though.

Before:



After:



WRT to your question: I voted somewhat prematurely "Leave it as-is", but in this particular case I'd probably follow [MENTION=84826]randyjawa[/MENTION]'s strategy and get a can of paint and a brush and repaint the bike.