This is one of those things that can frustrate the heck out of someone but is so simple it will immediately make you face palm. I thought it was worth a quick post....
All you have to do is select the paint tool (PT) and hover over the face you want to know about... This is what will pop up:
If you read the pop-up it says "Face:Painted with Brick Common"... Tah dah!
One last tip.. If you want to remove paint there is a little arrow next to the Paint button. When pulled down there is a new tool called "Remove Paint":