If you go to this page you can choose your color or choose random color when you create a challenge:
http://www.chess.com/echess/create_game
Personally I wouldn't care if a person only plays one color. Sometime I am hoping to play a certain opening, so if they want to play white that improves my chances of being able to play the defense I want to play.
would you play someone who insisted on always playing white? I wonder why they even have that option in open challenge