Play Colle system as black? I'm fascinated by the Colle system, but I'm not sure if it's applicable when you play as black.  Does anyone have experience in this?
Playing against 1.d4 a similar pawn structure to the Colle, but with reversed colors for black, leads to a defense known as the semi-Slav:

      [FEN ""]
      [Title "The semi-Slav"]
      1. d4 d5 2. c4 c6 {The Slav defense to the Queen's gambit.} 3. Nf3 Nf6 4. Nc3 e6 {The semi-Slav defense to the Queen's gambit.}


The main characteristic of said structure are the pawns on c6, d5 and e6, mirroring the ones on c3, d4 and e3 that characterize the Colle-like systems. The standard development for black also follows the general guidelines that are common in the Colle, that is, Bd6, 0-0 (although in some variations this move is delayed), Ngd7 and e4 when allowed.

This defense is a very well respected one, and it has been used as a drawing weapon by Viswanathan Anand many times. It has the drawback of needing a huge amount of theory in order to not fall behind in development and getting a passive position out of the opening. Players willing to play this need to have patience and accept playing in an somewhat inferior position for many moves before equalizing, and only then looking for an advantage.