Grate the beets in a food processor fitted with the shredding blade or by hand. Combine the shredded beets with the grapes. In a small bowl mix the orange juice, shallots, oil, lemon juice, tarragon and honey and season with salt and pepper if desired. Pour dressing over the beet and grape mixture and mix well. Line eight serving plates with the endive or lettuce leaves, divide the salad among them and serve.