Hi

I've: Chinese aftermarket head unit, Sirf Prima, 128Mb, 800x480

My Primo 2.0 2012 basemap preview screen has a really nice color scheme. Tan surroundings w/ a yellow road. Unfortunately, that is not one of my actual choices once I go to the Day/Night colors schemes.

Are there additional Day/Night schemes available.

Yes. Lots.
Often 3rd party skins come with additional color schemes, and many more are available at sites that specialize in such things such as igo8navigation.
You can also, with a little time and practice, make your own. Copy a {scheme}.zip file from the Content/scheme folder to your PC, open it, and you will see color.ini. It's a simple plain text file that defines all the colors for the various elements. Once you figure out what's what, you can change the colors to whatever you want using standard RGB values that can be determined from here if you are not familiar with them:
[Please Register or Login to download file]