These should make the grass/leaf tones much more realistic. Place these in the "misc" folder inside the minecraft.jar (on a mac, just put the misc folder in the same directory as the minecraft.app).
In cold areas, the grass will look dry and cold, in rainforests, the grass will be rich and dark, in deserts it will be dry and dead, and temperate grass is average colored. The leaves get dark and deadish looking in cold areas, in rainforests they are a dark and rich, in deserts they are dead and dry. I cannot make the edges follow the color, they do not change with the biome.