Q:

How to authorize colab with Github? 

When selecting option on Google colab "Save a copy on Github" I receive message : 

From reading https://medium.com/tensorflow/colab-an-easy-way-to-learn-and-use-tensorflow-d74d1686e309 this option should be available ?  
Should another an Github authorization link appear as part of above authorization popup ? 

A:

Saving notebook to github in colab is a simple two step process.  Just click Save a copy in github and authorize googlecolab for git. 
The first popup :

The second popup : (only if popup-windows are blocked in your browser)

The third popup : (click retry in second window OR it will open directly after first click)

Authorize and proceed.