When I first picked up the car, I could have sworn that the map background color changed from light to dark when the auto-headlights came on. Maybe I was just so excited and confused with all of the new features that I missed it?

I've read the manual, I've read the navigation manual and I can't find anything regarding the auto setting for the changing between light or dark, only the push button to manually change it.

What am I missing?

 

Not sure about your year but mine switches auto when the lights are on auto when they come on the navi switches background colors

 

The navi background will automatically switch to a darker color when you headlights come on, and revert back to the brighter color when your headlights go off. I found that if you are driving with the headlights on and you push the manual button to make the background lighter, it "de-activates" the automatic changes (even if you turn the car off and restart it). By pushing the manual button again, it will "re-activate" the automatic changes.

 

Maybe that's the issue then. I'll see what happens the next time I'm driving at night. Thanks!

 

If it's set to night when the headlights are on,or set to day when the lights are off... you're in Aotu mode and it should change automatically.
Otherwise, you're in manual mode and will need to hit the button once as LISI stated.