Ah, I see. I was thinking that if you used the gradient map method you may run into a bit of a continuity issue. The reason is that in your height map the mountain ranges (and the land surrounding them) in the north of your main continent have a very high elevation by comparison with the mountains to the south, or the island to the west. As a result the mountains in lower elevated areas will not have the same color scheme as those in the higher altitude areas. Perhaps that was what you were going for though.