The page "Flags of Vietnam: New Discoveries" at TTXVA website (https://www.ttxva.net/bieu-trung-viet-nam/) reproduces an illustrated text in French, most probably from Francia Vexilla, about the vexillological history of Vietnam, which contains, among others, the depictions of early religious/festival flags which are described as the "Emblems of Five Elements." They are square-shaped with serrated border, typical for Far Eastern flags. While the central field of each flag is in the color attributed to one of Five Elements, it is surrounded by four alternating white and black narrow frames, with a wider white border all around, while the serrated outermost border repeats the field color. Each flag is also accompanied by a long narrow pennant in the field color. In the flag image captions, black, red and yellow are correctly attributed to water, fire and earth, respectively, but white and blue (indigo), the latter used instead of the usual green, are mis-attributed to wood and metal, respectively, while it should be vice versa. The text also gives an incorrect list of colors - green, red, violet (called parme in French), white and black - followed by the list of Five Elements in order which corresponds to that of the images and their captions, regardless of the mis-attributions, but obviously does not correspond to the preceding list of colors.
The next paragraph describes the "standards of four directions" - that is, north, south, east and west - which are said to be green, red, white and black - again, the two lists' orders do not correspond to each other. In Far Eastern tradition, there is also the fifth direction - the center, symbolized by the color yellow, which is not mentioned in the text at all.
Both paragraphs certainly speak about the same set of flags, although the author has made a number of serious errors, as shown above. Still the correct reconstruction of these flags can be made, as follows:
- green flag for the element wood and direction east,
- red flag for the element fire and direction south,
- white flag for the element metal and direction west,
- black flag for the element water and direction north, and
- yellow flag for the element earth and direction center.
Green might have sometimes been replaced with blue, for the Far Eastern languages originally made no distinction between these colors. Violet color mentioned above would then probably be blue, changed by age and/or weather.
The original scanned text is accompanied by a modern rendition of these flags, where the field is charged with the inscriptions in Chinese, those in the four corners being the same on all five flags and those in the center being the names of elements - flag for the earth is erroneous, the field being made white instead of yellow. Each flag also has a wide border and a serrated edge, each of these in one of the other four colors from the list. Since the inscriptions are black, the element water is represented with color violet, but might have also been done because of Vietnamese dislike of the color black. Regardless of that, and of the errors as well, this image shows how the simple flags of five elements/directions, introduced from China, might have evolved into present-day five-colored Vietnamese festival flags, also known as the "Five Elements Flags," by adding decorative borders, originally in fewer colors, but eventually in all four colors different from the main one, resulting in a multitude of combinations, since no official design was ever prescribed. The black color, disliked in Vietnam, might have been eventually replaced with blue, or indigo, or violet, as seen in examples shown at this site:
Source: http://vexil.prov.free.fr/vietnam/vietnam.html Tomislav Todorovic, 22 February 2015