Both red miso and white miso are made basically in the same way. If the miso materials are steamed at high temperatures for a long time in the fermentation process, amino acids react with sugars, resulting in dark red miso. If the miso materials are boiled instead, the reaction is weak, and white miso is produced.
Many red miso is salty and have rich umami (good taste). Ingredients having distinct tastes, such as meat and shellfish, are suitable for red miso. On the other hand, white miso tastes mild, and it goes well with not only ordinary ingredients but also sweet ingredients, such as dumplings.