This function sets the current background color to the specified color. If the device cannot represent the specified color, it sets the background color to the nearest physical color.
This function fills the gaps between styled lines drawn using a pen created by the CreatePen function.
The SetBKColor function also sets the background colors for the ExtTextOut function.
If the background mode is OPAQUE, the background color is used to fill gaps between styled lines, gaps between hatched lines in brushes, and character cells.
The background color is also used when converting bitmaps from color to monochrome and vice versa.