Brown lentils are the most common kind, and sometimes the packaging will simply say u003cemu003elentils u003c/emu003erather than brown lentils. They're great for soup recipes because they hold their shape well. French green lentils are earthy and a bit nutty in taste and also hold their shape, so they would also work in this hearty lentil soup. Keep in mind green lentils cook a bit quicker than brown lentils, so adjust the cooking time accordingly. Red lentils are tender and fall apart easily, so choose from green or brown lentils instead if making soup.