I've had to add colour to a greyscale map in the past as well, and found it surprisingly challenging as well. But this came out very nice, good job!...
I'm a writer, i prefer using words to describe things rather than pictures, though quite recently I've come to realize that with some things pictures are more adept at describing things than words ever could. As of such i have chosen to join the Cartographer's Guild as a way to Augment my writing and hopefully expand my list of skills.