code: protected String colorString(int ir, int ig, int ib)
      {
      	return String.format("#%02x%02x%02x", ir, ig, ib);
      }
docs: Creates a CSS rgb() specification from the color component values.
  @param ir red value (0..255)
  @param ig green value (0..255)
  @param ib blue value (0..255)
  @return the rgb() string