tatfiend 

Historically, per Frank Berto, gumwall just means there is more rubber on the sidewalls than a "skinwall" tire has, regardless of tire sidewall color. Easier and cheaper to manufacture. Makes for a heavier tire with poorer rolling resistance theoretically. IMO really only counts with narrow high performance tires. Most all fully black colored tires, such as most Schwalbes, would probably fit your description as would most lower priced bike tires.