docs: public static String rgb(int r, int g, int b) {
      if (r < -100 || r > 100) {
        throw new IllegalArgumentException("Red value must be between -100 and 100, inclusive.");
      }
      if (g < -100 || g > 100) {
        throw new IllegalArgumentException("Green value must be between -100 and 100, inclusive.");
      }
      if (b < -100 || b > 100) {
        throw new IllegalArgumentException("Blue value must be between -100 and 100, inclusive.");
      }
      return FILTER_RGB + "(" + r + "," + g + "," + b + ")";
    }