I was talking about our banh chung, not your jung

Banh Chung goes in pair with Banh Giay.
Banh Chung is square and green, symbolizing the earth.
Banh Giay is round and white, symbolizing the sky.
The sky was viewed as pure, therefore it was given the white color
The earth was viewed as impure, full of trees and plants, therefore it was given the green color. (Note that agriculture was the main way of living of Vietnamese ancestors, therefore they associated the earth they lived on with plants).
On the earth, there were elements like fire, water, land, metal, woods. From what I read, the steps of making Banh Chung also go in the Cycle of the 5 elements.
In the center of banh chung is a red pork meat, the red color symbolizes fire.
The ashes from fire nourish the earth (or land).
The red pork meat is surrounded by a yellow bean paste. The yellow color symbolizes the earth.
Earth is where metals are found.
Surrounding the bean paste is the sticky rice of white color. The white color symbolizes metal.
Metal becomes liquid (water) when melted.
Which is why in the next step the whole cake is boiled in water.
Water nourishes plants (wood)
Which is why in the final step, the whole cake is wrapped in the green leaves. The green color symbolizes wood.
Banh Chung and Banh Giay go together to symbolize the harmony of the earth and the sky. The appearance of Banh Chung and Banh Giay in Vietnamese New Year signifies that the earth and sky are in harmony and the coming year will go well.
This is Banh Giay, symbolizing the sky


This is Banh Chung, symbolizing the earth