Harit, in his own thoughts…

<mx:Script>
	<!&#91;CDATA&#91;
		private function fill(event:MouseEvent):void
		{
			var data:BitmapData = Bitmap(imageObject.content).bitmapData;
			data.floodFill(event.localX,event.localY,0x00ffff);  // replace 0x00ffff with your choice of color
		}
	&#93;&#93;>
</mx:Script>
<mx:Image id="imageObject" source="...." click="fill(event)" />

This few lines simply fills selected or defined color to DisplayObject / Image like fill tool of any Paint tool.