There are many varieties of miso. They are classified by color (white, red, brown, and yellow), flavor (sweet or salty), and ingredients (usually depending on the type of grain used). Many Western miso manufacturers offer new types of miso with ingredients not found in traditional products; dandelion-leek miso is one example.
Darker miso, which is usually red or brown, tends to be more salty. White miso tends to have a somewhat sweeter flavor--although a salty flavor predominates in all types of miso. Yellow miso is light yellowish in color, has a salty flavor, and is usually made from rice and soybeans.
Miso can be smooth or chunky. Some Western companies produce a pasteurized miso that contains preservatives. Traditionally produced miso is unpasteurized and is aged over many months; it also has a better flavor and is widely available.