Nice map! (sorry, I don't really have much more to add.. i just like the way it looks and am curious as to how it will evolve )
On the colourtransition: assuming it's possible (i don't know what program you are using), perhaps pick a colour between the mountain grey and grass green, making the trnasition between colours seem less abrupt.
It seems that you have a light green surrounding the mountains in most cases, perhaps try a less saturated tint of green in between the grey and lighter green?
I'm curious to see the progress
And of course welcome to the guild!