How does segmenting a polyline into different colors work.

var viewer = new Cesium.Viewer('cesiumContainer');

var primitive = new Cesium.Primitive({
  geometryInstances : new Cesium.GeometryInstance({
    geometry : new Cesium.PolylineGeometry({
      positions : [
        Cesium.Cartesian3.fromElements(-2822918.76, -1347627.64, 5539750.33),
        Cesium.Cartesian3.fromElements(-2860091, -1790883.7, 6104936.09),
        Cesium.Cartesian3.fromElements(-2869994.31, -2212991.67, 6598178.01)
      ],
      width : 2.0,
      vertexFormat : Cesium.PolylineColorAppearance.VERTEX_FORMAT,
      colors: [Cesium.Color.RED, Cesium.Color.BLUE],
      colorsPerVertex: false
    })
  }),
  appearance : new Cesium.PolylineColorAppearance({
    translucent : false
  })
});

viewer.scene.primitives.add(primitive);