From the website: AKVIS Coloriage is as easy to use as a coloring book. No layers manipulation, no complicated techniques, no more hours of frustration attempting to get just the look you want - everything is done with a few brush strokes. Indicate the desired colors by the stroke of the brush; the program does the rest of the work: recognizes the object's border and tailors the new color to the grayscale tones of the initial picture.
Not cheap - $97
