ActionScript 3.0 :: Locate Multiple Positions Of A Specified Color In A Bitmap?

I'm building a game that will be using a bitmap to render the environmental scene. the bitmap is a black image with little green squares to indicate x,y place holders for tree locations as i render the scene. i was thinking of looping thru each pixel to find green pixels but this proves to be a performance hit when the image is 2500x2500. then i found what i thought was a handy little method called BitmapData.getColorBoundsRect() that will locate the position of the green box. It does this but it returns me 1 rectangle of all the green boxes inside.