There are two types of color fills in VCW VicMan's Photo Editor : the basic fill and the advanced fill.
The basic Fill fills the selected area or an area of similar color with the foreground color.
The advanced Fill fills the image up to the background color. It means that if you have a colored image with, say, strokes of light blue which is the current background color, then this tool will fill all the image (or a selected region) with the foreground color, leaving areas that have the background color intact.
Note