As the grid scrolls horizontally until the last column is totally visible, there is usually a blank area between the last column and the right border of the grid.

The color of this blank area depends on the setting of your system's 3D Objects color (or Button Face color). Eliminate this blank area with the ExtendRightColumn property. The default value of this property is False, but if set it True, the last column will extend its width to the right edge of the grid.