Please allow me to get the ball rolling and ask the first question, if you don't mind.

The dialogue listed below comes from Desperate Housewives, the first episode, season one.
ANDREW: I'm just saying, do you always have to serve cuisine? Can't we ever just have food?
BREE: Are you doing drugs?
ANDREW: What!?
BREE: (angry) Change in behaviour is one of the warning signs, and you have been as fresh as paint for the last 6 months. (looks down) That certainly would explain why you're always locked in the bathroom.
What does "as fresh as paint" mean here? I did some googling but failed to find out any similar expressions on the Internet. Is it a common expression in real lives or just a sort of new term created by the drama itself?