Yellow mustard is a paste made from the mature seeds of mustard greens, while green mustard is a paste made from the rhizomes of the wasabi plant. There is an essential difference between the two. There is a noticeable difference between the two, from color to taste. To be more technical, only yellow mustard is mustard, there is never such a thing as green mustard!

Yellow mustard is real mustard and a treasure passed down from our ancestors. It has become a common condiment around the common people as early as the Zhou Dynasty. It is ground from the seeds of mustard greens. When the mustard seeds are ground into powder, they become yellow "mustard", and when made into paste, it becomes mustard sauce.

Yellow mustard is an antique seasoning in my country, made from ground mustard seeds. It has been eaten for many years, so don’t think that mustard and horseradish are Japanese foods.

Green wasabi is the rhizome of wasabi, derived from wasabi in Japan. It is actually very expensive, so you often go to Japanese restaurants and five-star hotel buffets to eat the kind of wasabi (the toothpaste-like one used for salmon). The "wasabi sauce") is not real wasabi, but cheap horseradish. The taste of wasabi is actually not too spicy, and is even a little sweet. However, because its spiciness evaporates quickly, it is not easy to store and therefore expensive. Domestic stores rarely use it.

Reference: Baidu Encyclopedia-Mustard