Thanks very much, Christel!
Yeah... it's first time I did a cityscape, so I was not prepared for the tricky details
At the beginning I decided to do the windows by scraping. Recently I read in Ken Leslie's book about how he quickly did the windows by using this technique.
So this is how I started (and doing the sketch with the perspective in mind was tricky too - took me over an hour!)
I was in doubt whether it's a good idea to go light over dark, and yeah, the dark was showing through at the next stage...
I even thought it was a mistake to choose scraping (because of the dark grey showing through). And it turned out that just painting the windows dark grey is not enough - they looked flat and unnatural:
And this is the final image which you've already seen. I made the windows look better by using various dark and light colors to cover most of the dark grey. As for the dark grey base showing through, this was fixed by going over the darker spots with a light color to make it match with the main color of the building. And it worked well!
Though some of the light colors seem harder than others and they nearly peeled off the previous layer. It's all Mungyo OPs.
It was cumbersome indeed and it would probably have taken me the same amount of time to draw all the windows by hand, but... it was good to give it a try
and it's interesting that sometimes light goes over dark pretty well, like the ochre dots on the dark brown building on the right.