I know this topic has been up for discussion before and I have read everything I can. I am using some panels from Grafana that is displayed on my Magic Mirror. Like a wall dashboard. There is a special module for that.
However it is really annoying that the background is not black. I have modified the css but that only worked in Grafana 4. Now I have to rebuild the themes as far as I understand. I am using Grafana in Docker do that is not possible for me right now. Is there not any other way to hardcode the css directly so that the background is all black?
I had the same problem with MagicMirror + Grafana 6, now everything is just perfect 
Here is my solution: