Visualization rendering few points only

### Checklist

- [X] I have searched for [similar issues](https://github.com/isl-org/Open3D/issues).
- [X] For Python issues, I have tested with the [latest development wheel](https://www.open3d.org/docs/latest/getting_started.html#development-version-pip).
- [X] I have checked the [release documentation](https://www.open3d.org/docs/release/) and the [latest documentation](https://www.open3d.org/docs/latest/) (for `main` branch).

### My Question

Hey. I have an algorithm which iteratively colors points in the point cloud. I'd like to animate this algorithm by visualizing the point cloud and showing the points changing color.

I currently have it animated, but it is extremely slow since only a single point changes color each iteration and the entire point cloud is re-rendered each time. I could insert a handjammed fix where the point cloud only re-renders, say, every 20 iterations. But I'm wondering if there is a more elegant solution, perhaps one that capitalizes on the fact that only a single point changes color each iteration and there are no physical geometry changes.

Thanks!