Gogafem
I did a drawing sample for someone a week or two ago, I very quickly adapted it to do flood fills. It requires the Canvas plugin... not the cleanest code, because it started as a test by my 14 year old son - but it should give you some ideas.
left clicking draws with a brush, right clicking fills.
http://www.rieperts.com/games/forum/CanvasPainterFill.capx