Part of our France trip in October we are staying in Colmar for a couple nights than exploring black forest area in Germany and staying in Baden-Baden for a night before driving back to CDG to return car.
Are there any special requirements or permits driving to from that part of France thru Germany and back into France?
There are no requirements to cross the border, other than having a passport with you. Both countries are in the Schengen Area, there are no border controls, just roadside signs telling you that you have crossed the border.
The border in that area is the river Rhine. You cross by a bridge and the language used on signs and advertising changes, and the road signs and road markings are subtly different.
Some German cities require environmental stickers to enter with a car, but if you are staying out of big cities it will not be a problem.
German Autobahn do not have tolls, and none of the French Autoroutes in Alsace have tolls.
Here is a zoomable map of Germany where you need an environmental sticker (Umwelt-Plakatte).
https://umap.openstreetmap.fr/de/map/deutschlandalle_151247?scaleControl=false&miniMap=false&scrollWheelZoom=true&zoomControl=true&allowEdit=false&moreControl=false&searchControl=null&tilelayersControl=null&embedControl=null&onLoadPanel=undefined&captionBar=false#6/51.563/10.723
