Change shape solid color at runtime inside Drawable xml used as background

Found by me:

    View v = findViewById(R.id.layout_id);

    LayerDrawable bgDrawable = (LayerDrawable)v.getBackground();
    final GradientDrawable shape = (GradientDrawable)   bgDrawable.findDrawableByLayerId(R.id.shape_id);
    shape.setColor(----);