Adding multiple colors to CZML Line: Is it possible?

1. A concise explanation of the problem you're experiencing.
I am trying to give a CZML polyline file a multicolor property. The example from Brent Shanahan works within Cesium, but I would like add it to a file external to Cesium and load said file using Cesium.CzmlDatasource() load.
More specifically, how do I add VERTEX_FORMAT and more than one color to a CZML file?

Example Thread:!topic/cesium-dev/FKfcfuw2TpI

2. A minimal code example. If you've found a bug, this helps us reproduce and repair it.
//This is the code that works in Cesium:
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: true
  appearance : new Cesium.PolylineColorAppearance({
    translucent : false


/* The sections I am trying to get into the CZML file
* are vertexFormat and colors.

3. Context. Why do you need to do this? We might know a better way to accomplish your goal.
I am dynamically updating a CZML file during a flight and making the line color a gradient will improve readability as the line crosses itself repeatedly (it looks like a clump of red in certain locations).

4. The Cesium version you're using, your operating system and browser.
Cesium 1.43
Windows & Linux

The entity layer (and by extension CZML) does not currently support specifying colorsPerVertex. This is discussed as an open future enhancement here: