Change Background Base Map Color

Is it possible to adjust the download, or edit the file for a garmin520 so that the background or base map color isn’t white? I would like to change the background color to be black to save on battery.

Depends where did you get the download from, but generally it is possible by editing the TYP file.
You need a typ file editor (typviewer for example) and Javawa’s typchanger, see