code: 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 + ")";
    }
docs: This filter changes the amount of color in each of the three channels.
  
  @param r The amount of redness in the picture. Can range from -100 to 100 in percentage.
  @param g The amount of greenness in the picture. Can range from -100 to 100 in percentage.
  @param b The amount of blueness in the picture. Can range from -100 to 100 in percentage.
  @throws IllegalArgumentException if {@code r}, {@code g}, or {@code b} are outside of bounds.