Windsor was not used as a royal residence from the beginning.
The kings of that time preferred to use the former palace of Edward the Confessor (one of the last Anglo-Saxon English kings) in the village of Old Windsor for this purpose.
The imperial color was yellow. Almost all roofs in the Forbidden City have yellow glazed tiles
There are only two exceptions: the library in the Hall of Literary Brilliance has black tiles, and the residences of the Crown Prince have green tiles.