I need some help with Conditional Formatting, please.

I have a spreadsheet used to track data relating to reports prepared for
clients.  Column F on each row contains the date the report is due.   Column
G contains the actual date when the completed report is submitted.

I would like to add conditional formatting to Column F.   I can manage the
first part, which would add yellow background to cells with dates within the
next 3 days and red background to cells where the report is due today or
overdue.  

However, the part I am stumped on is: I would like to have no background
once any value is entered into column G.   Once the report has been
submitted, there is no longer any need to have color alerts, and it is not
helpful to have a bunch of red cells where the report has already been
submitted.