What do you mean by blue bricks and gray tiles?

Ancient bricks are burned blue and tiles are burned gray. There is a white wall behind the blue brick and gray tile. What I am talking about here is an ancient artistic conception, antique, antique. Generally, there are many ancient buildings with blue bricks and gray tiles in the south of the Yangtze River, and the most famous one is Old Huizhou. If you go to nature, feel the artistic conception of blue bricks and gray tiles.