Example:

const collection = new BufferPolylineCollection({
  primitiveCountMax: 1024,
  vertexCountMax: 4096,
});

const polyline = new BufferPolyline();

// Create a new polyline, temporarily bound to 'polyline' local variable.
collection.add({
  positions: new Float64Array([ ... ]),
  color: Color.WHITE,
}, polyline);

// Iterate over all polylines in collection, temporarily binding 'polyline'
// local variable to each, and updating polyline color.
for (let i = 0; i < collection.primitiveCount; i++) {
  collection.get(i, polyline);
  polyline.setColor(Color.RED);
}

See:

• BufferPolyline
• BufferPrimitiveCollection