All kinds! Red and split yellow lentils work particularly well for this easy dal recipe because they take very little time to soften and practically melt into the creamy stew. You could probably use green or brown lentils as a substitute here, but I haven’t tested it. Just know that green/brown lentils don’t soften as much as red lentils and will give the dahl more texture. They also take longer to cook, but you can mitigate this by adding more water or broth to the pot as needed.