code: public void setColorFill(PdfSpotColor sp, float tint) {
          checkWriter();
          state.colorDetails = writer.addSimple(sp);
          PageResources prs = getPageResources();
          PdfName name = state.colorDetails.getColorName();
          name = prs.addColor(name, state.colorDetails.getIndirectReference());
          content.append(name.getBytes()).append(" cs ").append(tint).append(" scn").append_i(separator);
      }
docs: Sets the fill color to a spot color.
  @param sp the spot color
  @param tint the tint for the spot color. 0 is no color and 1
  is 100% color