Vector is another method of saving images. A vector graphic saves points and their placement only, and the width of the lines connecting them. This also allows those vector images to grow/shrink and not loose resolution.
The other method is via bitmap or pixel. These type of images have to save a color associated with a small "box" or pixel.
There are advantages to both, but as for coloring it, after I've vector'd the lines, I bring it into Photoshop to color, which then rasterizes it and saves it as bitmap.