Selection handling is slow. How can I speed it up?

CesiumJS
1

I have a Sandcastle Link which demonstrates the problem.

I have many GeoJSON MultiPolygons. When this data is loaded into Cesium, each polygon becomes a separate entity. When I select, I need to:

  1. set selected MultiPolygon entities to the selected color
  2. set unselected MultiPolygon entities to the unselected color

Cesium then need to redraw.

The whole process taking 1 or 2 seconds. I am hoping it can be faster.

Is it possible to set the color of a group of entities?
What have I missed? Or, does this just take time?