The problem here I think arises in terms of what the color names mean vs. their RAL designation. Add to this the fact that model paint manufacturers often create their own descriptive names that have no bearing on official names and you get even more potential confusion. There isn't actually two different colors in terms of "chocolate brown" vs. "red brown" in what was ordered for use in the three-tone schemes.
The official wartime color was specified as RAL 8012. When you look up this color on modern RAL charts, it shows as "chocolate brown" but this isn't the same color that was used necessarily. The official German war-time name for RAL 8012 was Rotbraun or red-brown and not "Schokoladenbraun" or chocolate-brown.
If you look at the few surviving vehicle examples where the original paint is still present, the color darkness can vary...which most interpret to be down to the fact that the paint was issued as a paste and could be thinned by a variety of methods which in turn led to paint variation on the finished vehicle.
As dark as chocolate brown is, the only really appropriate time period for it's use is in the 1937-1940 two-tone scheme that calls for 1/3 "Dunkelbraun" to be used along with the standard panzer gray.