When you color a drawing with flood fills it's important to get a compression-free lined drawing to start with. If you flood fill a Jpeg, for instance, you'll find you are left with white spots unless you set the tolerance so high it starts eating the black lines. The alternatives are to start with a .Tiff drawing (no compression) or re-draw the lines digitally before inking.

I depaired of digital coloring when I first tried it because I was scanning the pics as Jpegs. Scan them as .tiffs instead, it helps a lot.

thanks strega, ill try that next time