Forbidden City was the administrative hub of Ming and Qing Dynasties. Chinese traditional philosophy including Five Elements, Five Directions, Five Colors, Four Symbols. Eight Diagrams, Yin and Yang, Tian Gan, Di Zhi, He Tu and Luo Shu was miraculously used in the construction of Forbidden City.
Dong Zhongshu recorded a special content in his masterpiece Chunqiu Fanmeng(春秋繁梦): Qinglong on the left (Wood), Baihu on the right (Metal), Zhuque in front (Fire), Xuanwu at rear (Water), Houtu at the middle area. In Hong Fan of Zhou Shu, the feature and the arrangement of Five Elements: Water, Fire, Wood, Metal and Earth. There are the associations among many things.
Five Elements: Wood, Fire, Earth, Metal and Water
Five Directions: East, South, Middle, West and North
Five Colors: Blue, Red, Yellow, White and Black
Four Symbols: Qinglong（青龙）, Zhuque（朱雀）, Baihu（白虎） and Xuanwu（玄武）
The connections among them are:
In Five Element Circulation Theory, these elements interact. Water creates wood; wood creates fire; fire creates earth; earth creates metal and metal creates water. Wood undermines earth; earth undermines water; water undermines fire; fire undermines metal; metal undermines wood. They circle and maintain the total balance of thing. The central symbol is earth, which is located at center. It is yellow and represents emperor. It means Power of Emperor. So the Forbidden City is yellow or golden yellow, which represents the earth and means the superiority of emperors.