Its original color scheme may be like this:
Theoretically, it refers to a color known as “qing (ching/青)”, which lies somewhere between blue and green.
This is because the military flags featured the traditional Chinese “Five Primary Colors (Wuzhengse/Wu-jeng-se)（五正色、五方色、五行色）” — qing (ching: blue-green), chi (chr: red), huang (yellow), bai (white), and hei (black) — corresponding to the Five Elements (Metal, Wood, Water, Fire, Earth) and the Five Directions (East, South, West, North, and Center).
From the time of the Zhou dynasty when the Book of Documents (Shangshu) was compiled, all the way to the final dynasty, the Qing, similar designs were used. Sometimes these were five separate monochrome flags; other times, they were combined into one five-colored flag.
This system of “Five Elements (Wuxing/Wu-shing), Five Directions (Wufang), and Five Primary Colors” even carried over through the late Qing navy, directly influencing the design of the national flag of the Republic of China, which was later associated with the ideology of “Five Races Under One Union.”
I would like to add that the Chinese themselves are often not clear about the color “qing”. Historically, the meaning of this word has expanded from dark blue that is almost black to light blue, blue-green, and even green. So in the “Five Colors Flag” of Chinese history, the flag representing the color “qing” could be green or blue. By the end of the Qing Dynasty, people generally accepted that qing and blue were similar. In some cases, you can also see green representing “qing”. In Japanese, this Chinese character directly refers to blue. But its original meaning is the color between blue and green in the picture.
There are two extreme cases called “qing”:
Therefore, this so-called “Jurchen flag” is most likely not a “flag symbolizing the Jurchens”, but just a kind of commonly used military flag in ancient China and cultural circles influenced by China (such as Korea and Vietnam), similar to the Taegeukgi, dragon flag, tiger flag, sun and moon flag, etc. It just happened to appear in this painting.
