There are 4 main types of lentils: brown, green, red and yellow. Brown and green are closest related and both hold their shape while cooking so best when not pureeing. Brown lentils cook in about 20 minutes where green lentils can take 30-40 minutes to fully soften. Red and yellow lentils are much softer and texture and break down where their shape is no longer recognizable. I would avoid using red and yellow in this recipe.