Mustard and horseradish are two different plants.

1. Mustard, also known as mustard, potato, mustard powder, is generally divided into two types: green mustard and yellow mustard. It is one of the most popular spices in the world with a long history. Horseradish, which belongs to the Brassicaceae family like wasabi, is a plant of the genus Horseradish

2. Horseradish itself is light yellow-white, and pigments are added to turn it green. The taste is similar to wasabi. The key is It's cheap. The common toothpaste-like "mustard" in China is actually not mustard, but horseradish.

Extended information:

Most people think that mustard sauce is made from a plant called mustard, just like chili sauce. But it's wrong. Mustard is a powdery condiment made from the seeds of mature mustard greens, Brassica genus Brassicaceae, generally yellow in color. It’s the yellow paste-like object that comes with the 3-dollar hot dogs sold by IKEA.

Horseradish is native to southeastern Europe and West Asia. In European countries, it is often used as a condiment for dishes such as roast beef. Because its taste is similar to wasabi root, it has become a material for imitation wasabi sauce. However, it does not belong to the Brassica or Wasabi genus but to the Horseradish genus. However, horseradish sauce itself is actually light yellow, and it needs to be dyed green with food coloring to become a copycat wasabi sauce.