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!...
Another small bit of progress - I closed the gap in the back row towards the east gate and began adding the castle at the west gate. Sadly i noticed...
So I wasn't going to enter this but I did decide to take a random spin myself and couldn't help my brain coming with ideas that I just had to draw.
...