Map Color (Day) and (Night) settings

I've been playing around with the NAV setup and here's the only things I haven't been able to truly figure out.

In the setup screen, page 4/4, you set the Map Color in day mode and Night mode. I've played with these things and can't see a difference. Ever. Am I that obtuse?

The manual references these settings on page 93, but there are no explinations or descriptions.

What are these settings and how does the Prius differentiate between daytime and nighttime in applying the settings you enter here? I was wondering if my headlights are throwing it off. I keep them on all the time. When it's dark outside and the map is overly bright, I adjust the Instrument Panel Light Control and the map switches colors. But no matter what settings I have them set to, the two modes always look the same.