How does the point cloud rendered by vtkPolyData interact with each point?

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5 
  const pointsNumber = points.getNumberOfPoints();

  const colors = new Uint8Array(pointsNumber * 3);

 for (let i = 0; i < pointsNumber; i += 1) {
    colors[i * 3 + 0] = 0;
    colors[i * 3 + 1] = 255;
    colors[i * 3 + 2] = 0;
  }

I realized color rendering in this way. I didn’t use the vtkColorTransferFunction class. How do I write it if I use this class? Also, I want to set the transparency of the point. How do I configure it