Its simply a list of what colours are used for vertex painting the ground in each region. I'm not claiming this to be something genius, it's just something ive found useful and I thought others may find it useful too.
Here are pictures showing the vertex paint used in http://dl.dropbox.com/u/22925394/tesannwyn-vclr-MORROWIND.png, and http://dl.dropbox.com/u/22925394/tesannwyn-vclr-BLOODMOON.png exported using TESAnnwyn by Lightwave
And here is a text file with the http://dl.dropbox.com/u/22925394/Region%20Vertex%20Paint%20Colours.txt
(Was clearer this way)
{S.G}