Well, I can't say I've ever come across that problem before. The only thing I can think of is if there's an incomplete wall you missed on the outside, but I'm pretty sure you would have caught that. Wall paint appears lighter or darker depending on the time of day if it's outside, or if there is just one gap in your building. In the second picture, I can see that the edges of your half walls are colored, so I'm assuming the top of the ones with glass are, too. In fact, I can see the glass ones making the cubicles are not dark like the ones making the balcony. My only suggestion is to make sure that you didn't leave a gap in your outer walls. Check the roofing, too. Any gap to the outside may be causing the problem. Hope this helps?