I don't know anything about how these murals were made. 1000yr old books do for the most part. Silver pigment will have turned grey, but other high quality pig

I don't know anything about how these murals were made. 1000yr old books do for the most part. Silver pigment will have turned grey, but other high quality pigments were often based on minerals that are still vibrant to this day. (Cheap pignents on the other hand were often organic, which would often not have lasted).