There are some lighter colored areas on hexes around the fields. Hex B1, for example. Is it some kind of road or just "decorative" coloration?
The coloration is that of "open ground". It is not a road.
While I don't have insight into the map art, I believe it was done to help give the allusion of fields on the map by breaking up the fields with open ground borders around each of the fields.
From memory, this generally will not have any impact on game play as there are very few sight lines (if any) that can occur down these non-field open ground strips.