One thing i found that helps with recoloring is to desaturate it first. Other wise the colors below seem to react with the new color. When i was trying to change that green, it ended up looking neon.

Of course now I'm trying completely different take on the map so it doesn't matter but its all still good info for later gimp use.

Now i'm off to sacrifice a goat in the hopes that the Wilbur gods will grant me a volcano. (I have spent more time trying to make this island volcano then i have on anything else lol.)