Please add a way to control the background color of the Label Style Composer (LSC) Preview and Text Component Editor (TCE) windows. It would be nice to specify this from inside the LSC.
I cover this in a post at the Autodesk Community Voices blog.
Link: Civil3d Leveraging Label Legerdemain a series "I Can See Clearly Now"
There is no setting or mechanism to control the Label Style Composer (LSC) background color.
The LSC Preview Window and Text Component Window inherit their background color from the tab that is current when the editor is invoked. The default C3D template uses a dark background for the model tab and a light background for the layout tabs.
I happen to use this convention. When I need the LSC, I pause and consider the label text color, make sure that a tab with an appropriate background color is current, then start the LSC.
Dark background (from Model tab) on the left and light background (from Layout tab) on the right: