You can enable here color inversion. All colors including the background color will be inverted.
You can use this function to enhance visibility of some drawings. The advantage is that all graphics operations can work correctly in this mode (in contrast to the Black Background mode). The disadvantage is that all colors (not only the background) are inverted (i.e. changed).
It is not recommended to combine this mode along with the Black Background mode, because this can be confusing (the color inversion changes the background to white, although the black background mode is enabled).
The key shortcut for switching the color inversion on/off is Ctrl-I. You can also add a corresponding button to the toolbar.
See also Black Background