code: public void setSelectorColor(int selectorColor) {
          this.mSelectorColor = selectorColor;
          this.mSelectorFilter = new PorterDuffColorFilter(Color.argb(mSelectorAlpha, Color.red(mSelectorColor), Color.green(mSelectorColor), Color.blue(mSelectorColor)), PorterDuff.Mode.SRC_ATOP);
          this.invalidate();
      }
docs: Sets the color of the selector to be draw over the
  CircularImageView. Be sure to provide some opacity.
  
  @param selectorColor The color (including alpha) to set for the selector overlay.