What about the color of the ancient house tiles?

Red walls and black tiles, mostly library buildings, are most afraid of fire and "black has mystery and leads to water", so they are covered with black tiles to prevent fire.

Most of the red walls and green tiles are the bedroom of the eldest son. The eldest son is a green representative because he needs to grow up in the future. Green represents wood and growth.

The residence of the son of heaven is generally red walls and yellow tiles ~