I approached you with this little problem way back and you wrote a little hook for me to correct it but I am now experiencing the same problem.
The home page is set out with a right-hand side bar which contains a widget that automatically displays an extract and thumbnail of the latest three blog entries. Thus the side bar does vary a little in height but usually the content window adjusts so that there is no gap between it and the footer. This is not happening at the moment so the background is showing.
As I said, this happened some years ago and you wrote the following snippet of code for the wp_footer hook:
<!– Requires Spacing 0.9 or GeneratePress 1.1.10 –>
Now I’m on Premium 1.8.3 so that may not be working. I’ve tried disabling it but there is no improvement.