It produces a “gradient” instead of filling it with color on cpp and neko targets, it works properly in flash and html5.
stage.color = 0x0000ff;
stage.addChild(new Bitmap(new BitmapData(20, 20, true, 0xfeff0000)));
When the alpha is 0x80 instead of 0xfe, it is only about 3 pixels long - it seems the color is alpha premultiplied repeatedly.