MessagePane background color


I use Thunderbird for a long while. Now I would like to change some minor things and started fiddling around with userChrome.css. For most elements I found a way to manipulate them to my liking.

But I could not figure out, how to change the background color of the message pane. I guess there is a mechanic in place which will force colors set in Thunderbird settings.

Background: I use the Conversations AddOn an it is quite useful to me. But a lot of times I can’t say which of the messages is collapsed and which not. I believe it is because of the same background color for the list and the list item. Therefore I would like to change the color by a few shades.

Is there anyway to do this?