Drawing: change the color of parts

[mspitz]

I do many assembly instructions.

To show the changes at each stage, I change the display style rooms:
- lines in grey for old parts
- black lines for new parts

My problem is : I can change the line color, the background is always white.
The idea is to change the background color of the pieces (white or + / - dark grey).

Here is an example of the results that I am seeking: