Indeed, weird thing. I can see color changed after editing the value in the foliage xml but nothing on the map. Starting a new game isn't a solution. At first I thought that the problem was you had only 3 values in the mapcolors (supposed to be 4 no ?) but adding a 4th didn't fix it in my test.
Btw, I saw on the map xml you have twice "animals" and "additionalfiles" blocks, it's time to clean up a little ;)