A few months ago, I did a post on what miso is. There are also different types of misos, and not all are interchangeable. I have found this out the hard way.
The color differences of miso can tell you the depth of flavor and level of saltiness to expect. The general rule is the darker the color, the stronger the flavor. Although there may be a few exceptions, depending on the brand or mixture.
Miso is made with soybeans, but there are some varieties that are a mix of soybeans and rice and/or barley. There is even a chickpea version that contains no soy. Soybeans are naturally gluten-free but miso is not always, it can be made with barley or other wheat ingredients. You should check the ingredients if you are allergic to gluten.
Miso is often labeled bycolor, white, yellow, red and brown. The colors come from a combination of the amount of time the miso is aged, as well as how the soybeans are cooked (steamed or boiled) and if there are other ingredients (like rice or barley).
White miso is generally the mildest and sweetest miso, followed by yellow, red and brown - the strongest and saltiest of the misos. Although I think some of the red misos are sweet too.
The white and red (sometimes) misos are an ok substitute for yellow miso. Most recipes that call for yellow or white miso only need a hint or of flavor and the brown miso is too strong. Red miso likely will alter the color of the dish if you substitute it in place of a yellow or white miso.
Brown misos won't work in HH recipes. Their flavor is too strong and different. If a recipe calls for brown miso, you can't really substitute it with a lighter color miso for the same reason.
Have you tried different colors of miso? Is there one you prefer?