Chicken and duck eggs turn into century eggs, revealing surprise colors—black, yellow, and patterned

I've been eating Chinese eggs since I was a child, but this is the first time I've made them myself. Grandma's house is in a remote place, surrounded by mountains and has a lot of land, there is always room to raise many poultry such as chickens, ducks, geese and rabbits. Most of my eggs come from my grandmother's house. This time when I visited him, I conveniently picked up a few chicken eggs to bring home, along with the duck eggs my grandmother had saved to make a batch of Chinese eggs. Northern herbs eggs are also known as variable eggs, their color depends on the temperature, time and ingredients used, but no matter the color, they are delicious!