From Stoik Software:
Color By Number lets you to convert photo to a paint-by-number pattern. Just scan the photo or load graphics file from disk, choose the brand of paints/crayons to be used and the program will convert your photo to a paint-by-number pattern optimized for the palette you have chosen. You can print the pattern together with color key. It often happens that particular paint palette contains too few colors to properly match colors in your photo. If you check 'Use mixed colors' option on the Colors dialog the program will look for best matching colors not only among pure palette colors, but among mixes of up to 3 colors from the palette. - Option to convert to the best matching RGB colors. This option allows the most accurate reproduction of colors, because the choice of best matching colors will not be limited by the colors available in the selected palette. You should not however that when you use this option it is not guaranteed that the colors in the pattern will be available in any of the paint palettes you may have. - Added Shaded palette The shaded palette (Shaded Carandache) contains several shades of each pure palette color. This allows better reproduction of photo colors even of the number of colors in the photo exceeds the number of pure colors in the palette.