We received a letter in the post from Elder Teal today. Part of the letter was a sketch of how Athens is divided into areas for the missionaries to work. The missionaries in the yellow areas are all one district assigned to the Greek speaking Branch The missionaries in the blue areas are the second district and are assigned to the English speaking branch.
I don't think that the areas have any relevance to where the apartments are.
It may not be the most accurate map of the suburbs of Athens
The missionaries in Greece only work in and around Athens and Thessaloniki as they are the two biggest areas of population and where there are chapels to attend.