Has anyone noticed all the blue roofs in satellite maps of North Korea and China? A quick search hinted that all industrial buildings are painted blue, much in

Has anyone noticed all the blue roofs in satellite maps of North Korea and China? A quick search hinted that all industrial buildings are painted blue, much in the way construction vehicles are yellow. At first glance, it looks like a mapping detail injected by Google Maps. Anyone have more information on these blue rooftops? Example (Sinuiju, North Korea): https://maps.google.com/maps?q=North+Korea&hl=en&ll=40.086855,124.378796&spn=0.011574,0.022724&sll=44.913398,-93.220024&sspn=0.085704,0.181789&oq=north+korea&t=h&hnear=North+Korea&z=16 https://maps.google.com/maps?q=North+Korea&hl=en&ll=...