[plt-scheme] Newbie question: Why "orange text, black background" after Run?

Matthias wrote:

> DrScheme tells you that you haven't tested certain parts of your  
> program. If you really don't want to know that you haven't finished  
> designing your program, you can open the language dialog, look at the  
> details, and turn off coverage. -- Matthias

I haven't succeeded in finding a place to turn this off. Can someone 
elaborate? Thanks. --PR