I'm using a map generator (Planet Map Generator) to create the landmasses, and then I am editing it in GIMP to make it a map.*

My first task is to clean the map up, which means I have to make all the land one color, and all the water one color (I can shade later). Unfortunately, all of the skins from the generator account for elevation and the colors use a gradient to show elevation. Which is very nice and wonderful, but it is a pain in the butt to go through and hunt down all the little tiny specks of water and change the color.

Does anyone know of a way in GIMP I can select an entire range of colors in the image and change them all at once?

*I don't currently have regular/easy access to a scanner, otherwise I'd hand draw my maps and then edit in GIMP.