I love the simplicity of these little buildings, but i wonder if even the slightest noise texture on them will make them feel less 'solid color'? The solid parts make it look a bit unfinished to me, while i can understand the desire for them to be clear and easy to read zoomed in/out but a bit of noise would go a long way to making it feel a bit tighter i feel.
Exaggerated and inverted noise (made this white instead of dark noise) to illustrate, it makes quite a difference if you notice the block of clear next the noise. Also don't overlay it over everything, subtle/moderated use is best. This is just a quick example of the impact