White miso is the product of soybeans after being fermented in a large rice percentage while red miso is made from soybeans that are fermented with barley. The fermentation process of white miso is faster as compared to the fermentation of red miso that requires a longer fermentation period. It is called white miso because the final product is white to light beige in color while the red miso ranges from red to dark brown in color.
White miso has a sweet taste that is usually used as mayonnaise or salad dressings while the red miso has a deep umami flavor that is perfect for braises, glazes, and soups. These two have a very distinct taste and color due to the length of fermentation.