siumerghe:

In China, yellow has long been associated with the Center – one of the five directions, along with the four cardinal points. Yellow was first perceived as the Emperor’s color during the Tang era (618-907), but not any yellow – only one particular hue: 赤黄, literally “reddish-yellow”. This rich and bright color was associated with the sun, and the sun was the symbol of the Emperor.

Initially, under the Tang, “reddish-yellow” was not forbidden for ordinary people to wear, and was not set by law as the Emperor’s color: wearing it was just the personal choice of some emperors. Then, during the reign of Emperor Gaozong,

“reddish-yellow”

was forbidden to be worn by commoners. In the Tianbao era (the second half of the reign of Emperor Xuanzong), the Emperor’s bedding, formerly purple, was replaced with

“reddish-yellow”, and the officials were forbidden to wear this color. It’s can be said that

in China

the perception of yellow as the Emperor’s color began from that period.

However, figurines and frescoes from the Tang era show that yellow

(just not the “reddish-yellow”)

was still very popular among the people of the Tang empire.

Also, during the Tang era, yellow, together with white, was one of the colors assigned by law to the lowest-level officials, soldiers, commoners and the like. Most yellow dyes are cheap, easy to produce and easy to apply to fabric, so in general yellow was considered a commoners’ color.

The Emperor’s yellow (“reddish-yellow”) vs the commoners’ yellow:

Still, the color of the Emperor’s ceremonial dress under the Tang was not “reddish-yellow” – it was, as in antiquity, deep black, combined with scarlet.

Tang Emperor with his retinue, a mural from Dunhuang:

Only in the Ming era (1368-1644) another variant of yellow – ocher 赭黄 – became the official color of the Emperor’s ceremonial dress, and both officials and commoners were forbidden to wear any shade of yellow. 

Under the Manchurian Qing Dynasty (1644-1912), ocher in the Emperor’s costume was replaced by a lighter and brighter hue – 明黃 “bright yellow”. 

Now this particular hue is still the one most strongly associated with the Emperor. In many dramas and movies, Emperors of the pre-Qing dynasties wear “bright yellow”, however, this is historically incorrect.

I’d like to add that the fact that some color was considered the Emperor’s color didn’t mean that the Emperor was doomed to wear only it. While the Emperor’s ceremonial dress had to conform to the color regulations (Tang – black with scarlet, Ming – ocher, Qing – bright-yellow), in their daily life Emperors were free to wear any color they liked.