enlarging the red-yellow-green buttons at the top of the active window

Is there a way to do this? I'm trying to help an older woman with a new mac book pro and while I can get nice big clear icons in Firefox (as opposed to Safari) and set default fonts larger than usual, pointer larger than usual etc, there are still those tiny little close-shrink-enlarge buttons at the top of the active window. Any way to fix that?

Thanks!