I think there are already enough topics about an eraser tool (and yes, that would be awesome), but I couldn't find anything about a two colour system like it can be found in f.e. paint and the likes. If I want to draw a pool of water, that is impossible with the current tools because it would just be an array of blue circles/squares that are empty white inside. With a fill colour I would not have to redo parts of the map outside of roll20 (using dungeonographer) but could just add stuff like that to it, replacing the formerly black or white map ground. It would also make it possible to differentiate and create basic tiles as we already have quite an array of colours at our disposal.
