According to official Google documentation, to change the color of grid you need to right something like
{vAxis: {gridlines: {color: '#f0f'}}}
Even if I use same library
<script type="text/javascript" src="https://www.gstatic.com/charts/loader.js"></script>
The code above does not work. Instead I found and I use
{vAxis: {gridlineColor: '#f0f'}}
Can anyone explain why the official documentation is wrong ?