After reading the Cities and the Rural Economy on page 86, I am wondering what the colour coding means?

Red: dedicated largely to the feeding of the city. These lands are intensively cultivated to maximize the production of foodstuffs – mainly cereals and vegetables. Most manors specialize in just a handful of crops in an effort to achieve economies of scale, peasant holdings generally are smaller and more land is cultivated as part of the main estate. Firewood (as charcoal) is also an important product from these estates. As these estates have access to urban goods of generally better quality and lower price, they employ few craftsmen of their own and dedicate as much labour as possible to farming.

So what does the Yellow, Blue, and Green represent? Was the description cut from the final edit.

Would be handy to know, especially since it impacts the economy for Aléath.