On U.S. highways, green signs with white text are generally for navigational information: Upcoming exits and junctions, freeway entrance and exit signs, and street signs.

They are green so that a human's eyes will get distracted by the color and it will look at the sign.

be prepared for workers and slow moving equipment

To freeway to freeway to have to do what you do.

When you exit the freeway just follow the signs to the rental car return, and it will show where you go for each company.