[Inkscape-user] Inverting Parts of a black and white graphic

Hello,

is there a good way to invert a black and white graphic in inkscape.

As an example, take

https://github.com/Bouni/MDT-Glas-Push-Button-Template/blob/master/MDT-Glast...

and invert the upper or the lower graphic.

I tried to add a layer and use exclusive-or with a black box overlay, but I it did not do at all what I was hoping for (xor between black and white).

Is there a good way to do that without changing the color of every item?

I am an inkscape beginner, so every advice is welcome :-)

Many thanks Rainer