Conditional formatting for difference between target date and today's date

Good morning all (sorry my first thread has to be probably a fairly straightforward request!)

I've been asked to create a database for our quality assessment schedule and doing so requires a 'countdown' effect for the target date of the next assessment. I'm using =TODAY() to give today's date in G2 at all times, and I want the target date boxes to be shaded:

• RED if the target date is within 30 days
• YELLOW if the target date is between 30-60 days
• GREEN if the target date is between 60-90 days (maximum possible range)

I have figured that I can only do "this month" or "next month" on the standard CF options, but I'm sure there must be a pretty simple code/formula for doing what I want to achieve. I've tried messing around with =DAYS and =IF but don't know enough about these formulae to get it right.

I've attached a dummy worksheet for help with reference.

Thanks in advance for any pointers!

Rob