In Revit previous version, when using the paint tool, you had to click the Modify | Paint tab and then select the material from the Material drop-down. And if you want to remove paint, you had to activate the Paint tool and choose <By Category> from the Material drop-down.
In Revit 2012, select the paint tool will open the Materials dialog, where now you can visually preview materials and access material properties in order to modify a material. You can see your changes without closing the Materials dialog.
Also, you can use the “Remove Paint” tool to remove a material that has been applied to a face.
Meanwhile, you can identify the quantities of materials used as Paint in material takeoffs.